basic physics notes by atul waghmare

8/11/2019 Basic Physics Notes by Atul Waghmare

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Chapter - 1

Properties of solids

Q- Define Elasticity & Plasticity OR State Elasticity & Plasticity

Property

Ans: Elasticity: Elasticity is defined as a property of the body by virtue of

which it tends to regainits original shape or size on removal of deforming

force.

Plasticity:Plasticity is defined as a property of body by virtue of which it

does not regainits original shape or size on removal of deforming force.

Q- Define Restoring Force & Deforming Force

Ans: Restoring Force: The force which changes the shape & size of the

body after its application.

Deforming Force:It is an external forcewhich changes the shape & size of

the body after its application.

Q -Define Stress.State its types

Ans: Stress:It is defined as internal restoring force per unit cross sectional

area of a body.

S. I. unit N/m2

Types of Stress

(1) Longitudinal or Tensile stress

(2)

Compressive or Normal stress

(3)

Volumetric or Volume stress

(4) Shearing or Shear stress


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Q. Define following terms

(1) Tensile stress

(2) Compressive stress

(3) Volumetric stress

(4) Shear stress

Ans: Tensile stress:The stress when applied results in change in the length

of the body is called as tensile stress

Compressive stress:A stress which causes an elastic body to shorten in the

direction of the applied force is called as compressive stress.

Volumetric stress:The stress when applied results in change in the volume

of the body is called as volumetric stress.

Shear stress:The stress when applied results in the change in shape of the

body is called as shear stress

Q. Define Strain. State its types

Ans: Strain:It is the ratio of change in dimension to original dimension of a

body. It has no unit

Types of Strain

(1)

Tensile or longitudinal strain

(2) Volumetric or volume strain

(3)

Shearing or shear strain


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QDefine following terms

(1) Tensile Strain

(2)

Volumetric Strain

(3)

Shear Strain

(4) Breaking Stress

Ans: Tensile Strain:Tensile strain is defined as the ratio of change in length

per unit original length of a body

Volumetric strain: Volumetric strain is defined as the ratio of change in

volume per unit original volume of a body.

Shear strain:It is defined as the ratio of lateral displacement of any layer to

its distance from fixed layer.

Breaking stress:The maximum stress at which the wire breaks is called as

breaking stress.

QState Hooks law of elasticity

Ans :Statement :Within the elastic limit stress is directly proportional to

strain Stress Strain

Stress = Constant x Strain

Stress = M x Strain

Where, M - constant of proportionality called as

modulus of rigidity

QDefine elastic limit

Ans: It is defined as maximum stress which can be applied on a body

without permanent deformation of a body.


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Q Define Youngs modulus, Bulk modulus, Modulus of rigidity.OR

Define three elastic constant & state the relation between them.

Ans: Youngs modulus:It is the ratio of tensile stress to tensile strain

Tensile stressYoungs modulus (Y) =

Tensile strain

Bulk modulus:It is the ratio of volume stress to volume strain

Volume stress

Bulk modulus (k) =Volume strain

Modulus of rigidity:It is the ratio of shearing stress to shearing strain

Shearing stressModulus of rigidity () =

Shearing strain

9k Relation: Y =

3k+

Where,Y = Youngs modulus

k = Bulk modulus = Modulus of rigidity

Q Define following: Factor of safety, Yield point, Ultimate stress,

Compressibility

Ans: Factor of safety:It is defined as the ratio of ultimate stress to working

stress

Yield point:The point on stress Strain curve at which plastic flow begins

is called as yield point


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Ultimate stress:It is the maximum stress (force per unit area) the material

can withstand before it breaks

Compressibility:The reciprocal of bulk modulus of elasticity is called as

compressibility.

C = 1/K

QGive relation between bulk modulus of elasticity & compressibility

Ans: Compressibility= 1/ Bulk modulus

QDefine Poissons ratio

Ans: It is defined a within elastic limit the ratio of lateral strain to

longitudinal strain.

It is denoted by Lateral strain

= = -d / D

Longitudinal strain l /L

QState the factors affecting on elasticity

Ans: Factors affecting on elasticity

(1)

Change of temperature

(2) Effect of hammering & rolling

(3) Effect of annealing

(4)

Effect of impurities


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QExplain the behaviour of a wire under continuously increasing load

by using stress strain diagram.

Explaination

A graph or diagram of stress and strain is shown as above.

OE Portion is straight line which indicates that stress is proportional to

strain. Therefore the wire obeys Hookes lawupto the point E this point is

called elastic limit.

EE Portion is curved towards strain axis this shows that increase in strain is

more, than increase in stress. In this region stress is not proportional to

strain.

Between any point E and E if all load is removed then some permanent

elongation / increase in length takes place in the wire this is called set.

When wire is again loaded, a new straight lineSEis obtained which obey

Hookes law.

Some portion after the point Yis almost parallel to strain axis this shows that

strain increases without increase in stress just like wire flows. This is called

plastic flow.

The point at which the plastic flow begins is called yield point.


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CHAPTER2

Properties of Liquids

Fluid Friction

QDefine

1. Pressure

2. Atmospheric Pressure

Pressure:It is defined as the force acting on a unit surface areaor The force

per unit area is called as pressure

Ex:Nail with pointed tip can easily penetrate in the wall

Pressure (p) = Force (F)

Area (A)

S. I. Unit N/M2or Pascal (Pa)

Atmospheric Pressure:The Pressure exerted by the atmosphere is called as

atmospheric pressure.

QState Pascals law

Ans: Statement :It states that, in an enclosed liquid, if pressure is applied

at any part of the liquid, then this change of pressure is transmitted

undiminished to every portion of the liquid & to the walls of its container

QState Archimedes Principle

Ans: Statement: It states that when a solid insoluble body immersed

completely or partly in a liquid, it loses its weight & loss of weight of the

body is equal to the weight of displaced liquid.


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QDefine Critical Velocity

Ans:It is defined as the maximum velocity of liquid up to which its flow is

streamlined is called as critical velocity.

QDefine

(1) Viscosity

(2)

Velocity gradient. State its S.I. unit

(3) Coefficient of viscosity.State its S.I. unit

Ans: Viscosity:The internal force developed between two layers of a liquidwhich opposes (resist) the flow of liquid is called as viscosity

Ex:Glycerine, Honey, water

Velocity gradient: It is defined as the ratio of change in velocity to the

corresponding change of distance S. I. unit is S-1

Coefficient of viscosity:

Theviscous force developed between two liquid layers of unit surface area

& unit velocity gradient is called as coefficient of viscosity.

S. I Unit is N-s/m2

QState Pressure depth relation. Give meaning of each terms in it.

Ans: Pressure depth relation, P = h g

Where, pPressure

gAcceleration d due to gravity

Density of liquid

hPressure head


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QState Newtons law of viscosity

Ans: Statement:The viscous force (F) developed between two liquid layers

is

(i)

Directly proportional to the surface area of liquid layer (A)

(F A)

(ii)

Directly Proportional to velocity Gradient (dv/dx)

i.e. [F (dv/dx)]

F A dv/dx

F = A dv / dx

QDefine thrust (force). State its S.I. unit

Ans: It is defined as the total force exerted by a liquid on a surface incontact is called as thrust of a liquid. S.I. Unit - Newton ( N )

Q. Define streamline flow & turbulent flow with examples

Ans : Streamline Flow : The flow of liquid in which every particle of

liquid move in same direction (parallel) of flow of liquid is called as

streamline flow.

Ex: water flow through tap, canal flow, flow of river during summer

Turbulent flow: The flow of liquid in which particle of liquid does not

move in same direction (random) of flow of liquid is called as turbulent

flow.

Ex:River flow during flood, Whirlpools, water fall


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QDistinguish between streamline flow and turbulent flow

Streamline Flow Turbulent Flow

1. The velocity of liquid is smaller

than critical velocity

1. The velocity of liquid is greater

than critical velocity

2. For this Reynolds number is less

than2000

2. For this Reynolds number is

more than 3000

3.There is no mixing of various

layers with each other

3.There is always mixing of various

layers with each other

4.It is a steady flow 4.It is speedy flow

5.All the molecules of liquid move

in same direction

Ex-Canal Flow, flow of river during

summer

5.All the molecules of liquid do not

move in same direction

Ex-Water fall, river flow during

flood, whirpools

QDefine Reynolds Number. State its formula with meaning

Ans: Reynolds Number: Reynolds Number is a non dimensional Number,

used in fluid mechanics to determine whether the flow is streamline,

turbulent or unstable.

Vc = R / rd

Where, Vc = critical velocity of Flow of liquid

d = density of liquid

r = radius of the tube

= coefficient of viscosity of liquid


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QGive the significance of Reynolds number

Ans : Significance of Reynolds number

1.

When R 3000, the flow of liquid is turbulent.

3. WhenRis in between 2000 to 3000the flow of liquid is unstable.

QDefine terminal velocity & upthrust force

Ans: Terminal velocity:It is defined as the constant velocity with which thebody is freely falling through the liquid column.

Upthrust force: It is defined as the force acting on body completely or

partially immersed in liquid that causes apparent loss in weight of the body.

QState Stokes law of Viscosity

Ans: Statement: It states that for a small spherical body falling freely

through a liquid, the viscous force is directly the viscous force is directly

proportional to the,

1. Radius of the sphere. (r)

2.

Terminal Velocity (v)

3. Coefficient of viscosity of liquid ()

F r v

F = Constant x (r v )

F = 6 r v

Where, 6 is the constant of proportionality


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QState the effect of temperature and adulteration on viscosity

of liquid

Ans It is observed that as temperature of liquid increases, its viscositydecreases

i.e. Viscosity 1Temperature

When adulteration such as soluble substance is added to liquid, its viscosity

goes on increasing

i.e. viscosity adulteration

QDerive an expression for coefficient of viscosity by stokes method

Ans: Consider a small sphere of radius r and density falling freely

under gravity through viscous liquid as shown in (Fig.)

After covering certain distance through the liquid, metal sphere attains an

constant velocity called terminal velocity.

Metal sphere falling freely through a liquid experiences two forces as shown

in (Fig.)

Downward force = Weight of metal sphere

= Volume of metal sphere x density of metal sphere

= 4/3 r3x g x (1)

Upward force of two types.

(a) Upthrust force = Loss of weight of body in a liquid


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= Weight of displaced liquid (by Archimedes principle)

= Volume of sphere x density of liquid

= 4/3 r3

x g x .(2)

(b) Force of viscosity

F = 6 r v (3)

When a metal sphere attains terminal velocity.

Total upward force = Total downward force

4/3 r3x . g + 6 r v = 4/3 r

3x .g

6 r v = 4/3 r3((- ) g

4 x x r3

x (- ) x g =

3 x 6 x r x v

= 2 / 9 r2x (- ) x g

v ....(4)

Equation (4) gives coefficient of viscosity by stokes method.

QWrite two applications (examples) of Pascals law

Ans: Hydraulic press To compress metal sheets

Hydraulic brakesUsed in cars, buses

Hydraulic jackTo lift vehicles in workshop, cars, jeeps


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Surface tension

QDefine surface tension. Write its S.I. unit

Ans: Surface tension:It is defined as the force acting per unit length of an

imaginary line drawn to surface of liquid.

S.I. unit is N/m

Q State the effect of temperature and contamination on surface

tension of liquid

Ans: Effect of temperature: The surface tension of the liquid depends on

temperature. Surface tension decreases with increase in temperature

Surface tension 1 / temperature

Effect of Contamination (impurity)

In most of the liquid surface tension decreases with increase in

contamination

Surface tension 1 / Contamination

QDefine cohesive & adhesive force

Ans : Cohesive force :It is the force of attraction between two molecules of

same substance

ExForce of attraction between two water molecules

Adhesive force: It is the force of attraction between two molecules of

different sub stances

ExForce of attraction between water moleculeand glass molecule


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QState the applications of surface tension

Ans: Application of surface tension

1.

For manufacturing of bullets or ball bearings which are spherical2.

Oil with low surface tension are used as lubricants, in soap or

detergents

3. Water rises up to the leaves of plants due to capillary action

4. Oil rises up in wick in oil lamp by capillary action

5. To check purity of water

QDefine angle of contact. State its S.I. unit

Ans : Angle of contact :The angle between the tangent to the liquid surface

at the point of contact & the solid surface inside the liquid is called as angle

of contact.The S.I. unit of angle of contact is radian

QDefine Capillarity. Give examples of capillary phenomenon (Action)

Ans : Capillarity : The rise or fall of the liquid in capillary tube due to

surface tension is called as capillarity & the phenomenon is called as

capillary action

Examples of capillary action

1.

Oil rises up to the end of wick of lamp due to capillarity

2. A blotting paper absorb ink due to capillarity

3. Rise of ink through pen nib

4. Water rises from stem of tree towards the branches by capillary action

5. Damping of bricks


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QExplain Laplaces molecular theory of surface tension

Ans: Diagram

Explaination:

Laplaces molecular theory of surface tension

1. Consider three molecules M1, M2 & M3 of the liquid. A sphere of

influence is drawn as shown in fig.

2. The sphere of influence of molecule M1 is completely inside the

liquid, so it is equally attracted in all directions by the other molecules lying

within its sphere. Hence the resultant force acting on it is zero.

3.

The part of the sphere of influence of molecule M2 lies outside the

liquid & the major part lie inside the liquid. Therefore resultant force acting

on it is directed downward.

4.

For molecule M3half of its sphere of influence lies inside the liquid

and half lies outside the liquid. So, the maximum resultant downward force

is acting on molecule M3


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5.

Thus molecule M1 experiences zero resultant force, M2 experience

downward resultant force, M3experience more downward resultant force. In

short moleculesbelow imaginary line PQ experience zero resultant force

and moleculesaboveline PQ experience some or more downward resultant

force.

6. Thus molecules which lie on the surface of liquid (surface film)

experience downward resultant force and are being pulled inside the liquid.

To balance this downward force, molecules come closer to each other. This

reduces the surface area of liquid.

7. This gives rise to surface tension. It is the contraction force which

decreases the surface area of the liquid.

Q State the relation between surface tension, capillary rise, radius of

capillary tube with meaning of symbol used in it.

Ans : Relation between surface tension, capillary rise and radius of

capillary tube

T = rhdg / 2 cos

Where, T = Surface tension

r = radius of capillary tube

h = rise of liquid

d = density of liquid

g = gravitational acceleration

= angle of contact


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QDerive an expression for surface tension by capillary rise method.

Ans: Consider a capillary tube of radius r vertically inserted into a liquid.

The liquid rises to a height h and forms a concave meniscus. The surface

tension T acting along the inner circumference of the tube exactly supports

the weight of the liquid column.

By definition, surface tension is the force per unit length acting at a tangent

to the meniscus surface. If the angle between the tangent & the tube wall is

, the vertical component of surface tension is cos .

Therefore, the total surface tension along the circular contact line of

meniscus is 2 r T cos .

Upward force = 2 r T cos .Where,r is the radius of the capillary.

The downward force on the liquid column is due to its weight which is

m x gthus,

Downward Force = m x g

Downward Force = r2h d g

At equilibrium condition,

Upward Force = Downward Force

2 rT cos = r2 d g

r h d g

T =

2 cos

This is a expression for surface tension of a liquid in a capillary tube.


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CHAPTER3

Thermal Properties of Matter

Modes of Transformation of Heat

QDefine Heat & Calorie

Ans: Heat : Heat is a form of energy which gives us the sensation of

warmness and hotness. S. I. unitJoule

Calorie: The amount of heat required to increase the temperature of one

gram of water by one degree Celsius is called as calorie

S.I. unit0K

QDefine absolute zero temperature

Ans: Absolute zero temperature: The temperature at which pressure &

volume of gas theoretically becomes zero is called absolute zero

temperature

Absolute zero temperature = O0A = - 273

0C

QWhat is kelvinscale of temperature?

Ans: In this scale, the lower fixed point is 2730C & upper fixed point is

3730C& it is then divided into 100 equal Parts, each part is called as degree

Kelvin.

QDefine Celesius (centigrade) scale of temperature

Ans : In this scale of temperature, lower fixed point is considered as 00Cand

upper fixed point as 1000Cand it is then divided into 100 equal parts, each

part is called as degree Celsius or centigrade.


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QDefine Fahrenheit scale of temperature

Ans : In this scale of temperature, lower fixed point is 320Fand upper fixed

point is 2120

Fand it is then divided into 180equal parts, each part is called

as degree Fahrenheit.

QState & explain the modes of transmission of heat OR

Define three modes of transmission of heat with examples OR

State the three ways in which heat is transferred from one place to

another with one example of each.

Ans :Conduction :It is the process of transfer of heat from a part of body at

higher temperature to a lower temperature without actual movement of

particles of medium

Ex:Heat sink in electronic circuits, safety lamps, ICE boxes etc.

Convection:It is the process of transfer of heat from a part of body at higher

temperature to a part of body at lower temperature with actual movement of

particles of medium.

Ex:Formation of trade winds, Room ventilation system, monsoons etc.

Radiation:In this process, heat is transferred directly from a body at higher

temperature to the body at lower temperature without necessity of

intervening medium

Ex:Use of white clothes, heat radiators in car, in activation of HIV etc.


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Q Distinguish between conduction, convection & radiation process.

Ans:

Conduction Convection Radiation1. It is the process of

transfer of heat from a

part of a body at

higher temperature to

a part of body at lower

temperature without

actual movement of

particles.

1. It is the process of


part of a body at

higher temperature to

a part of body at lower

temperature with

actual movement of

particles.

1.It is the process of


body at higher

temperature to a body at

lower temperature

without necessity of

intervening medium

2. If metal rod is

heated at one end, its

other end gets heated.

2. Heating of water in

a beaker.

2. Heat from sun reaches

the earth

3. Material medium is

essential.

3. Material medium is

essential.

3. Material medium is not

essential.

4. Metal rod itself acts

as a medium.

4. Liquid itself acts as

a medium.

4. Medium may be

present like air or no

medium. i.e. vacuum.

5. It has applications

likeHeat sink in

electronic circuits,

Safety lamp, Ice boxes

etc

5. It has applications

like- formation of

trade winds, room

ventilation system,

monsoons etc.

5. It has applications like-

use of white clothes, heat

radiators in car, in

activation of HIV etc


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QState the law of thermal conductivity

Ans: The amount of heat (Q) conducted is,

Directly proportional to area of cross section of the rod (A)

Q A ------------(1)

Directly Proportional to the temperature difference between the two

surfaces of the conductor

Q

(1 - 2) ------------(2)

Directly Proportional to the time for which heat flows

Q T ------------(3)

Inversely Proportional to the distance between two surfaces

Q 1/d ------------(4)

Q A/d (1 - 2) t

Q = k A (1 - 2) t / d

QDefine coefficient of thermal conductivity. State its S.I. unit.

Ans :Coefficient of thermal conductivity is defined as the amount of heat

conducted normally across unit cross sectional area of a material of unit

thickness in one second, when the temperature between its ends is unity

S. I. unitJoule / mok


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QState application of

1. Conduction of heat

2.

Convection of heat

3.

Radiation of heat

Ans: Applications of Conduction:

1. Good conduction material is used as a heat sink in electronic circuit

2. Use of thermos Flask

3. Condenser coil in a refrigerator is ideally made up of copper

4.

Davys safety lamp

5.

A bad conducting material like thermocole is used in ice box.

6. Handle of cooker is made up of bad conducting material

Applications of Convection:

1.

Ventilation in the Room

2.

Cooling system in automobile engine

3.

Formation of land & sea breeze in the nature

4. Formation of trade winds

5.

Gas filled coiled electric lamp

6. Monsoons

Applications of Radiation:

1.

Electric bulb, the sun

2. White clothes absorb less heat so they are used is summer

3.

The teapot & kettle have clean & bright shining surface

4. Aeroplanes & ships are painted white.

5. Base of cooking utensils is made black.

6.

Heat radiators in car, machines are painted black


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QDefine good conductor & bad conductor with examples.

Ans : Good conductor :The material which conduct heat easily from it is

called as good conductor

Ex:Iron, Copper, Silver

Bad conductor:The material which does not conduct heat easily from it is

called as bad conductor.

Ex:Wood, Wool, Glass, Thermocole

Q Why we do not receive heat from the sun by conduction. Give

reason.

Ans: Conduction needs medium for transfer of heat. Between the sun and

earth the millions of kilometres there is no medium present. Hence

conduction is not possible

Q - Distinguish between heat and temperature

Heat Temperature

Heat is form of energy which gives

sensation of hotness and warmness

S.I. Unit Joule

Temperature is the measure of

degree of hotness or coldness of a

body S.I. UnitKelvin

Heat is the cause Temperature is the effect

Heat flows from higher

temperature to lower temperature

Temperature is the condition that

determines the direction of flow of

heat

Heat is an extensive property Temperature is intensive property


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Gas laws

QDefine three gas law OR

State Boyles law, Charlesslaw and Gay Lussacs law

Ans: Boyles law:At constant temperature, volume of given mass of a gas

is inversely proportionalto its pressure

i.e. V 1/p

i.e. P1 / V1= P2 / V2= Constant, at constant temperature

Charles law: At constant pressure volume of given mass of a gas is

directly proportionalto its absolute temperature

i.e. V T

i.e. V1 / T1= V2 / T2= Constant, at constant pressure

Gay Lussacslaw: At constant volumepressure of given mass of a gas is

directly proportional to its absolute temperature

i.e. P T

i.e. P1 / T1= P2 / T2= Constant, at constant volume

QDefine specific heat of substance.

Ans: It is defined as the amount of heat required to increase the temperature

of 1kg mass of a substance through 10C

S.I. UnitJkg-1


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QDefine the two principal specific heats of gas OR Define Cp and Cv

OR Define specific heat of a gas at constant volume & at constant

pressure

Ans: Specific heat of a gas at constant volume (Cv):It is defined as the

amount of heat required to increase the temperature of unit mass of a gas by

10C at constant volume

Specific heat of a gas at constant pressure (Cp):It is defined as the

amount of heat required to increase the temperature of unit mass of a gas by

10

Cat constant pressure

QState ORDerive General (Perfect) gas equationwith meaning of eachsymbol

Ans: According to Gay Lussacs law

P T ------------------- (1)

According to Charles law,

V T --------------- (2)

Combining equation (1) & (2)

PV T

PV = RT--------- (3)

Where RUniversal gas constant

PPressure of gas

VVolume of gas

TAbsolute temperature

Eqn(3) is called general (perfect) gas equation


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QDefine isothermal change & adiabatic change

Ans: Isothermal change: The Process in which volume of a gas changes

keeping its temperature constant is called as isothermal change

Adiabatic change: The process in which volume of a gas changes with

change in temperature is called as adiabatic change

QDifferentiate between isothermal and adiabatic process

ISOTHERMAL PROCESS ADIABATIC PROCESS

Volume & pressure changes at

constant temperature

Volume & pressure changes at

changing temperature

Gas filled in is a good conductor

of heat

Gas filled in is a bad conductor

of heat.

Transfer of heat takes place. There is no transfer of heat.

Volume changes are made

slowly

Volume changes are made

rapidly

Gas obeys Boyles law i.e.

PV =constant

Gas does not obeys Boyles law

Here PV r = constant

Expansion of gas takes place Compression of gas takes place

Ex.Boiling of water Ex.Bursting of cycle tyre


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QWhy Cp is greater than Cv?

Ans :(1) When gas is heated at constant volume the heat supplied is utilized

to increase the temperature of the system

(2) But when gas is heated at constant pressure, the heat supplied is utilized

to increase the temperature of system as well as for doing the work in

expanding a gas at constant pressure

So, Cp> Cv

Q State the relation between the two specific heats of gas give the

meaning of symbols used in it

Ans: Relation: CpCv = R/J

Where, Cp-Specific heat of gas at constant pressure

Cv-Specific heat of gas at constant volume

R- Universal gas constant

J-Joules constant

QDerive Mayers relation OR Derive the relation Cp - Cv=R/J

Ans:When the gas is heated at constant pressure, the internal energy (K.E.)

of the gas increases, and the gas expands, so that it performs some external

work in expansion of the gas.

i.e. Cp= CV + H

Cp- CV = H


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But H = W/J [Joules law]

Cp- CV = W/J

But W = P (V2-V1)

Cp- CV = P (V2-V1) /J

Cp- CV = (PV2-PV1) /J

But PV1 = RT1& PV2= RT2

Cp- CV = R (T2-T1) /J

Now if T2 - T1= 10C

Cp- CV=R/J

This is the Mayers relation for one mole of gas

QWhat is NTP and STP ?

Ans: NTP means normal temperature and pressurewhereas STP means

standard temperature and pressure


30/46

CHAPTER4

OpticsRefraction of Light

QDefine

1) Critical Angle (Qc)

2) Total Internal Reflection

Ans: (1) Critical angle: The angle of incidence for which the angle of

refraction is equal to 900C is called as critical angle.

(2) Total Internal Reflection: The phenomenon in which a ray of light

travelling from denser medium to rarer medium is totally reflected in denser

medium, if the angle of incidence is greater than critical angle of medium is

called as total internal reflection (TIR)

QDefine

1. Numerical Aperture (NA)

2. Acceptance Angle (a)

Ans: Numerical Aperture (NA):The sine of maximum acceptance angle is

called as numerical aperture

Acceptance angle (a) :The maximum value of external incident angle for

which light will propagate in the optical fibre is called as acceptance angle.

Q - Define refraction of light

Ans: When a ray of light travels from one medium to another it deviates

from its original path is called as refraction of light


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Q Draw a neat labelled ray diagram for refraction in case of prism.

State the prism formula with meaning of each terms used OR

QDerive Prism formula

Ans: Diagram

Let PQ be the incident ray obliquely incident on refracting face AB. At point

Q the ray enters from air to glass therefore at Q the incident ray is refracted

and travels along QR by making r1as angle of refraction.

At point R the ray of light enter from glass to air and get refracted along RS.

From E Q R

= x + y

= (i-r1) + (e-r2)

= ( i + e) - (r1+ r2) -----(1)

From Q D R

r1 + r2 + QDR=1800

-------------(2)

As AQDR is cyclic quadrilateral

A + QDR=1800

-----------------------(3)

By comparing eq. (2) and (3)

A = r1 + r2 ---------------------------(4)Substituting above value in eq.(1)


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Eq. (1) becomes

= ( i+e)-A

+ A = ( i+e)--------------(5)

If = m

i =e

And r1 = r2 =r

Equation (5) Becomes

A + m = i + i

A + m = 2i

A + m

i =

2

And equation (4) becomes

A = r + r

A = 2r

Ar =

2

According to snells law

sin i

=

sin r

Substituting values of i and r in above equation

Sin A + m

2 Where, m = Angle of minimum deviation

= A = Angle of prism

Sin A / 2 = Refractive index of prism


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QState Snells law with its mathematical equation

Ans : Snells law :For any two media the ratio of sine angle of incidence to

the sine angle of refraction is constant.

This is known as Snells law

Equation:

Sin i

= Constant

Sin r

Where, Sin i = angle of incidence

Sin r = angle of refraction

QState laws of refraction

Ans: 1.Incident ray and refracted ray are on opposite side of the normal

2.The incident ray,the refracted ray and the normal ray at point of separation

of two media lie in the same plane.

3.For any two media the ratio of sine angle of incidence to the sine angle of

refraction is constant.This is known as Snells law

Q- State the principle of optical fiber

Ans: The optical fiber works on principle of Total Internal Reflection

i.e. when monochromatic light is obliquely incident on the interface

between optically denser medium and rarer medium and if angle of incidence

is greater than critical angle then no refraction take place and only reflection

take place.


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Q - Describe the stucture of optical fiber.

Ans: Optical fiber consists of three major parts

1.

Core: The inner most co-axial region is core. It acts as the guide

for the light. The diameter of the core is 10-100m. It is made up of

glass having high refrative idex.

2. Cladding: The core is surrounded by a glass or plasticcladding. Its

refractive index is lessthan that of the core.

3. Sheath(polymer jacket): The outermost protective regionof the

fiber is called sheath. It is made up of polymer. It protects the core

from contamination, moisture etc. It provides mechanical

strengthto the fiber.

Q - Derive the expression showing the relation between numerical

aperture and acceptance angle.

Ans: As shown in fig.

A light ray launched into an optical fiber in air at an input angle less

than the acceptance angle for the fiber

Applying snells law at the air-core interface.

sin i / sin r = 2/ 1 i.e. 1sin i = 2sin r ---(1)


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but from fig.

sin / sin (90 c) = core / air

airsin = coresin (90 c)

sin = coresin (90 c) ( air =1)

sin = core cos c [ cos c = sin ( 90- c)]

sin = core 2 c)

2

sin = core 1- cladding

core

sin2

core -2

cladding = NA

This is the relation between Acceptance angleand Numerical

Aperture.


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CHAPTER5

Wave Motion

QDefine

1. Amplitude (a)

2. Period (wave period) OR Time Period (T)

3.

Frequency (n)

4. Velocity (V)

Ans: 1. Amplitude (a) : The maximum displacement of a particle of the

medium from its mean position on either side is called as amplitude of the

wave

2. Wave period (T):The time taken by a wave to complete one oscillation is

called as wave period.

3. Frequency (n) :It is the number of vibration, performed by the particle in

one second

4. Wavelenght:It is the length of one full wave OR

The distance travelled by the wave to complete one vibration or oscillation is

called as wavelength

5. Velocity (V): The distance travelled by the wave per unit time is called as

velocity of the wave.

QState the relation between velocity, frequency & wavelength

Ans : Relation: V = n

Where, V = Velocity

n = Frequency = Wavelenght


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QDefine simple harmonic motion. Give examples of SHM

Ans: It is defined as the periodic motion of a particle in which the force is

always directed toward mean position & its magnitude is proportional to its

displacement from mean position.

Examples of simple harmonic motion

1. Motion of pendulum

2. Motion of needle of sewing machine

3. Oscillations of spring

4.

Vibration of string

5.

Oscillations of piston in a cylinder

6. Oscillations of magnetic compass ( needle )

QDefine Phase angle & Epoch in S.H.M.

Ans: Phase angle: The angle which gives position, direction and

displacement of the particle in S.H.M at any instant is known as phase angle.

Epoch:Initial phase angle or starting phase is known as epoch

QDefine Longitudinal waves & Transverse wave with example. OR

Define progressive wave state type of progressive wave. Define the type.

Explain two types of progressive wave.

Ans: Progressive wave: The wave which continuously travels in a given

direction is called as progressive wave.

There are two types of progressive wave

1.

Transverse wave2.

Longitudinal Wave


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Transverse wave: The waves in which particles of the medium vibrate

perpendicular to the direction of propagation of the wave are called as

transverse wave.

Ex Light waves, electromagnetic waves, vibration produced by streched

string of sitar, violin, sonometer

Longitudinal Wave:The waves in which particles of the medium vibrate

parallel to the direction of propagation of the wave are called as longitudinal

wave.

Ex - Sound wave, waves in organ pipe, waves set in kundts tube

QDistinguish between Transverse wave & Longitudinal wave

Transverse Wave Longitudinal Waves

The wave in which direction of

vibration of particles of medium isperpendicular to the direction of

propagation of wave is called

transverse wave.

The wave in which direction of

vibration of particles of mediumis parallel to the direction of

propagation of wave is called

longitudinal wave.

Wave travels in form of alternate

crests and trough

Wave travels in form of alternate

compressions and rarefactions.

Density and pressure of medium

remain same throughout the wave

Density and pressure of medium

changes.

Wave travels through solid only. Wave travels through liquids and

gases.

Ex. Light waves Ex. Sound waves


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These wave can undergo

polarization

These wave do not undergo

polarization

QDistinguish between progressive waves and stationary waves

Ans:

Progressive waves Stationary waves

There is transfer of energy in

the direction of propogation ofwave.

There is no transfer of energy.

All particles vibrate with the

same amplitude.

All particles vibrate with

different amplitude.

All particles of the medium are

vibrating.

Particles at nodes do not vibrate

at all.

Every particle vibrates with

different phase.

Velocity of wave not zero

All the particles in one loop are

in same phase.

Velocity of wave is zero

QState superposition principle (theorem)

Ans: Superposition theorem: When two or more waves travelling through

a medium arrive at a point simultaneously, each wave produces its own

displacement at that point independently of the other wave. Hence, the

resultant displacement at that point is the vector sum of the displacements

due to each of the waves.


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QState how stationary waves is formed OR Define stationary waves

Ans: Stationary waves are produced when two exactly identical progressive

waves having same amplitude, same wave length & same speed travelling

through a medium along the same path in exactly opposite directions,

interfere with each other. The resultant wave produce due to super positions

of these two waves is called as stationary wave.

Q Give the condition for Resonance effect in sound OR Define

Resonance ORWhat is resonance effect

Ans :Condition for resonance effect:When the frequency of the external

periodic force applied to a body is exactly equal to natural frequency of

body, the body vibrates with maximum amplitude, then resonance effect

takes place & the phenomenon is known as resonance

QGive two examples of Stationary waves

1. Wave formed on the string stretched at both the ends

2. Waves formed on sonometer wire

3. Waves formed in air column of resonance tube

QGive two examples of Resonance1. When the speed of a car increases beyond a certain limit different parts

of the car begin to vibrate due to resonance & large noise is produced.

2. In a sonometer, resonance occurs when the natural frequency of the

vibrating length of the wire equals the frequency of the tuning fork

3. In Resonance tube experiment, resonance occurs when the length of

the air column is adjusted such that the natural frequency of the air column

equals the frequency of the vibrating tuning fork


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QState the characteristics ( Properties ) of stationary waves

Ans : Characteristics of stationary waves

1.Nodes and antinodes are formed alternately.

2.

There is no transfer of energy.

3. Pressure is maximum at nodes and minimum at antinodes.

4.

Distance between any two consecutive nodes or antinodes is equal to

/ 2

5. The distance between a node and its adjacent antinodes is equal to / 4

6. Particles in the same loop vibrate in the same phase.

7.

Particles in the adjacent loop vibrate in the opposite phase.

QDefine free vibration & forced vibration with examples

Ans: Free vibrations (oscillations): The vibrations performed by a body

when only once disturbed from its equilibrium position and vibrates with a

natural frequency are called free vibrations.

Examples:

1.Cricketers hanging ball

2. Vibrating tuning fork

3. Vibrations of air column

Forced vibration (oscillations): When a body is continuously disturbed by

a periodic force, then the particle cannot vibrate with its natural frequency

but it starts vibrating with the frequency of periodic force. These vibrations

are called forced vibrations.

Examples:

1. Concrete bridge in earth quake

2. Vibrations of air column under vibrating tuning fork3. Kid swinging after applied external periodic force.


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Q Derive equation of simple harmonic motion OR Obtain an

expression for motion of a particle performing SHM.

Ans: Cosider a particle P moves with a uniorm angular velocty along a

circular path of radius a. Let M be the projection of referenceparticle Pon diameter AB. Therefore M is performing S.H.M. Let the

displacement of M from O is x, then t = 0, the reference point is at

Po

So that, m < POPo=

In time t, reference particle moves from Poto P.

Such that, m < POPo= = t

Draw PM on diameter AB.

Since, OC is parallel to PM

< OPM = < POC = ( t + )

From fig, in OPM

Sin ( + ) = x/a

i.e. x = a sin ( t + )

This is equation of particle performing simple harmonic motion


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Q - Which is more elastic steel or rubber? Why? OR Why steel is more

elastic than rubber?

Ans: Steel is more elastic than rubber. Because steel comes back to its

original shape faster than rubber when the deforming force is removed

Q - State the factors affecting angle of contact of liquid/fluid OR On

what factors angle of contact depend?

Ans:Nature of liquid, nature of solid, purity of liquid and cleanness of liquid

are the factors affecting angle of contact of liquid

Q - Give the significance of angle of contact

Ans: Significance of angle of contact

1.

In case of water in glasscontainer, is acutebecause force of adhesion

is stronger than cohesion

2.In case of mercury in glass container, is obtusebecause force of

cohesion is stronger

3.If liquid completely wetthe solid then = 0

4.

If liquid does not wetthe solid then is obtuse

5.If liquid wetthe solid then is acute

Q - Define rigidity

Ans: The property on account of which a body does not change its shape and

size even when a large force is applied on it is called as rigidity


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basic physics notes by atul waghmare

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