physics laboratory - ii - marmara...

T.C. MARMARA UNIVERSITY

FACULTY OF ARTS AND SCIENCES PHYSICS DEPARTMENT

PHYSICS LABORATORY - II

DEPARTMENT: NAME: SURNAME: NUMBER:

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T.C.MARMARA UNIVERSITY PHYSICS DEPARTMENT

PHYSICS LABORATORY –I I MANUAL

EXPERIMENT NO:

EXPERIMENT NAME:

THE DATE:

GROUP NO:

NAME:

NUMBER:

DELIVERY TIME:

REPORT NOTE:

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EXPERIMENT.1

OHM’S LAW & SPECIFIC RESISTANCE OF A CONDUCTOR

Goal:1.) Introduction to electrical conductivity

2.) Parameters which effect on conductivity, definition of resistance and parameters which effect on resistance

3.) Introduction to simple components of an electrical circuit and building circuit

4.) Introduction to basic electronic device and using in a circuit

Theory: Resistance of a conductor is proportional with lenght of wire and specific resistance. There is an inverse ratio between cross-sectional area of the wire and resistance of the conductor at the same time. Resistance’s unit is ohm(Ω) in SI unit system.

Figure.9 – A simple circuit

A simple electric circuit can be built as Fig.9. Power source supply potential difference -which known as voltage- in the circuit. The voltage unit is Volt (V). Electrons that enter from negative edge to circuit pass through resistance and move to the positive edge. In this way, these electrons generate a current in circuit. According to Ohm’s Law V=I.R, if we increase voltage, we get more current in the circuit.

Experimental Setup:

Apparatus: 1.)Board 2.)Various resistances 3.)DC voltage source 4.)Digital multimeter 5.)Connectors 6.)Conductor metal wires that have various cross-sectional areas

lR

A

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EXPERIMENTAL SETUP AND MEASUREMENTS:

Build circuit given at right side on board.

Measurements: Firstly connect conductor wires have different cross-sectional area and lenght values to place shown in the figure and then change potentiometer value for constant applied voltage. For every changing, record current value in the wire and potential difference between edges of wire to the table. 1. Type of

Wire: Diameter of Wire (m2):

Length of Wire(m):

2. Type of Wire:

Diameter of Wire (m2):

Length of Wire(m):

V(V) I(A) ρ(Ω.m) V(V) I(A) ρ(Ω.m)

1. 1.

2. 2.

3. 3.

4. 4.

5. 5.

6. 6.

3. Type of Wire:


Length of Wire(m):

4. Type of Wire:


Length of Wire(m):

V(V) I(A) ρ(Ω.m) V(V) I(A) ρ(Ω.m)

1. 1.

2. 2.

3. 3.

4. 4.

5. 5.

6. 6.

Calculations: 1.) Measure and record length of wire with ruler. 2.) Measure and record diameter of wire with micrometer for cross-sectional area of wire.

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3.) Calculate and write on the table specific resistance of wire for each voltage value. 4.) Calculate resistance of wire for every measurement. 5.) Using the formula that give specific resistance value, derive relative error formula and calculate maximum absolute error. 6.) Draw I-V plot and calculate specific resistance value via the graphic. 7.) Compare specific resistance values that you get with the values in the literature-can be found in appendix table- then determine your percentage error. 8.) Interpret your conclusions.

EXPERIMENT 1. OHM’S LAW & SPECIFIC RESISTANCE OF A CONDUCTOR -NOTES:

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EXPERIMENT NO:

EXPERIMENT NAME:

THE DATE:

GROUP NO:

NAME:

NUMBER:

DELIVERY TIME:

REPORT NOTE:

3

3

EXPERIMENT.2

SERIAL-PARALLEL CONNECTION OF RESISTANCES & EQUIVALENT RESISTANCE CALCULATING

Goal:1.) Calculation of equivalent resistance

Theory: Calculating Equivalent Resistance: Resistances may connect to circuit serial or parallel. Equivalent resistance of circuit can be calculated with formulas given below for serial or parallel connection.

( ) 1 2 3 4eq serialR R R R R ( )

1 2 3 4

1

1 1 1 1eq parallelR

R R R R

In a serial circuit, current and voltage on each resistance is:

In a parallel circuit, current and voltage on each resistance is:

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Experimental Setup:

Apparatus: 1.)Board 2.)Various resistances 3.)DC voltage source 4.)Digital multimeter 5.)Connectors


1.) Calculate resistance’s value that you will use via the table and measure them with multimeter.

2.) Connect resistance as schemes above. Measure and record equivalent resistance by multimeter before apply voltage to circuit.

3.) Apply ‘supply voltage’ to all of circuit.(Max. 5V)

4.) Build four connection scheme that given below on board and measure voltage value on each resistance. Calculate passing current and fill the table.

Scheme(1) V 1: V2: V3:

R 1: R2: R3:

I 1: I2: I3:

Equivalent resistance 1:

Scheme(2) V 1: V2: V3:

R 1: R2: R3:

I 1: I2: I3:


Scheme (3) V 1: V2: V3:

R 1: R2: R3:

I 1: I2: I3:


Scheme (4) V 1: V2: V3:

R 1: R2: R3:

I 1: I2: I3:


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Figure 1- Parallel - Serial Connection of Resistances

Calculations:

1.) Calculate equivalent resistance for each scheme and compare initial equivalent resistance value with the value you get. Then calculate your percentage error.

2.) Compare current passing all branches of circuits and voltage on all branches of circuits with total current passing in circuits and applied voltage on whole circuit. If there is a difference, specify reasons of this difference.

3.) Build serial and parallel circuits randomly and then measure their equivalent resistance. Later, compare these values with your theorical values.

4.) Interpret your conclusions.

Experimental Theorical

Req1:

Req2:

Req3:

Req4:

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EXPERIMENT 2. SERIAL-PARALLEL CONNECTION OF RESISTANCES & EQUIVALENT RESISTANCE CALCULATING-NOTES:

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EXPERIMENT NO:

EXPERIMENT NAME:

THE DATE:

GROUP NO:

NAME:

NUMBER:

DELIVERY TIME:

REPORT NOTE:

3

3

EXPERIMENT.3

NON-OHMIC DEVICES IN A CIRCUIT-1

Goal:1.) Investigation of current-voltage characteristic of non-ohmic devices in a circuit

Theory: Resistance of non-ohmic devices is not constant and it changes with as a function of current. For example, in one of the non-ohmic devices, filament bulbs, if we rise current, it emit more light and wire in the bulb gets hot. If we draw current-voltage graphic of these devices, we observe a non-linear character. Similarly, dynamic resistance value of this filament is represented by dV/dI. Current-voltage characteristic of another non-ohmic devices, diode, is shown right side and its dynamic resistance is:

Dd

D

Vr

I

Static resistance is obtained from specific current that correspond specific DC voltage for static resistance. It is a dynamic resistance that observed around forward voltage point. Current passes in organic diodes and LED’s only one way. They may show high or low resistance depending on polarity of applied voltage. LED’s are conductor for forward voltage and they can conduct very small current(~mA) for reverse voltage. –This small current is known as ‘leakage current’.- LED’s emit light with only forward voltage.

Filament bulb is getting hot while current is passing on it so it must be observed that resistance is how depends on temperature. Resistance of bulb is changing with temperature as formula given below. α is temperature coefficient for tungsten.

R=Rroom[1+α(T-Troom)]

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Experimental Setup:

Apparatus: 1.)Board 2.)Filament bulb 3.)DC voltage source 4.)Digital multimeter 5.)Connectors


1.) Build the circuit shown figure above.

2.) Connect a small resistance on the branch that connected to bulb. This prevent heating and burning of the bulb.

3.) Apply max. 6 V DC from power source to circuit and increase the voltage step by step.

4.) Write the values that you read amperemeter and voltmeter that connected to resistance and bulb to the table.

Voltage(VR)

Voltage(VB)

Current(A)

5.) Draw I-V graphics for voltage and current values you read on resistance and bulb. Calculate static resistance via slope of the graphic you get.

6.) Calculate resistance of bulb for maximum voltage.

7.) Calculate power of bulb for the maximum voltage.(P=V2/R)

8.) Calculate resistance of bulb at room temperature using the graphic you drew for bulb.(Find resistance from the point that intersect graphic minimum voltage and current scala.)

9.) Record the temperature of your laboratory.

10.) Calculate temperature coefficient for tungsten wire using resistance value you found for maximum voltage. You can use resistance-temperature formula.

Note: Temperature coefficient for tungsten is 4.5 10-3 K-1 .

11.) Calculate your percentage error for temperature coefficient you found.


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EXPERIMENT.3 NON-OHMIC DEVICES IN A CIRCUIT-1-NOTES:

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EXPERIMENT NO:

EXPERIMENT NAME:

THE DATE:

GROUP NO:

NAME:

NUMBER:

DELIVERY TIME:

REPORT NOTE:

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EXPERIMENT.4

NON-OHMIC DEVICES IN A CIRCUIT-2

Goal: 1.) Investigation of current-voltage characteristic of one of the non-ohmic devices, diode, in a circuit

Theory: We will continue to investigate non-ohmic circuit devices and study I-V chracteristic of diodes.

Diodes are semi-conductor devices. Their I-V characteristic are not linear by contrast with resistances and passing current increase with increasing temperature. Basicly, diodes made by two semiconductor material that have different charge carrier concentration and this structure known as p-n junction.

A simple p-n junction is shown in figure below.

Electron concentration is more in N area just as hole concentration is more in P area. When these two different semiconductor constitute a junction and this junction connect a circuit as below, electrons pass the junction and move to positive edge. Theotically hole moving is defined, but actually only negative charged electrons move. A diode behaviour is shown below for feed-forward.

In backfeed area, electrons and holes split up to different poles cause of applied back voltage on junction. So a consumption area is formed at junction.

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Edges of diode are named as in figure. Impurity atom concentration in a diode desingnate the diode working as rectifier or zener. Rectifier diode do not show any resistance for feed-forward and show high resistance for backfeed. Zener diode show high resistance for positive or negative voltage. A voltage on diode is constant value.

When backfeed voltage reaches a value that named breakdown, rectifiers do not work anymore but zeners do. This is basic difference between zener and rectifier.

Experimental Setup:

Apparatus: 1.)Board 2.)Zener diode 3.)DC voltage source 4.)Digital multimeter 5.)Connectors 6.)Si or Ge diode


1.Rectifier diode:………………………………………….

1.) Backfeed:

1.) Build circuit right side for silicon diode and connect resistance to circuit.

2.) Increase applied voltage and read voltage on diode and current pass in circuit. Then record them to table.

2.) Feed-forward:

3.) Connect the diode to circuit for feed-forward and increase applied voltage. Read current and voltage values and record it.

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2.)Zener diode:……………………………………………..

1.) Backfeed:

1.) Build the circuit for zener diode and connect resistance.

2.) Increase applied voltage and read voltage on diode and current pass in circuit. Then record them to table.

2.) Feed-forward:

3.) Connect the diode to circuit for feed-forward and increase applied voltage. Read current and voltage values and record it.

4.) Draw I-V characteristic for rectifier and zener using feed-forward and backfeed values together.

5.) Determine working voltage for rectifier and zener diode on the graphics.

6.) Determine breakdown voltage for diodes on the graphics.

7.) Explain electrical conducting mechanism when we apply feed-forward and backfeed voltage on P-N semiconductor diode.

8.) Research current conduct capacity of diodes using in technology. What are the factors that desingnate conductivity? Explain what we can do to increase efficiency of diodes shortly.


1.Rectifier diode

Feed-forward Backfeed 2.)Zener Diode:

Feed-forward

Backfeed Feed-forward

Backfeed

1.) Volt(V) I(A) Volt(V) I(A) 1.) Volt(V) I(A) Volt(V) I(A)

2.) 2.)

3.) 3.)

4.) 4.)

5.) 5.)

6.) 6.)

7.) 7.)

8.) 8.)

9.) 9.)

10.) 10.)

11.) 11.)

12.) 12.)

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14.) 14.)

15.) 15.)

16.) 16.)

17.) 17.)

18.) 18.)

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EXPERIMENT.4 NON-OHMIC DEVICES IN A CIRCUIT-2-NOTES:

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EXPERIMENT NO:

EXPERIMENT NAME:

THE DATE:

GROUP NO:

NAME:

NUMBER:

DELIVERY TIME:

REPORT NOTE:

3

3

EXPERIMENT.5

CAPACITOR CHARGE-DECHARGE CHARACTERISTICS

Goal:1.)Understand the working principles of the capacitor

2.)Investigate the charge and decharge characteristics of capacitor

Theory:

Basicly a capacitor can be built by placing two metal conductive plate face to face in a small distance. Then the plates are connected to a voltage source and when the potential is applied one of the plates are charged +Q ,while other is –Q. The voltage difference between two plates are approximately V applied potential. Capacitance is the ratio of the charge to the potential difference between the plates. It is shown by “C” and in SI unit system its value is Farad (F).

Capacitance of the capacitor:

0

QC

V

AC

d

C :capacitance

Q :net charge

V :potential difference between the plates

ε0 : electric constant (ε0 ≈ 8.854×10−12 F m–1)

A :plate area

d:distance between plates

When the plates are connected by a conductive wire the electrons from the negative plate will move to the positive plate and the plates will be notr. There will be no charge in

http://en.wikipedia.org/wiki/Vacuum_permittivity

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each plate if it is waited enough and capacitor will be decharged. There will be an electric field between the charged plates and this field can be gives as due to Gauss Law;

0E

σ :the surface charge density on the plates

The potential difference between the plates;

V Ed

If we want to increase the capacitance of the capacitor a dielectric material can be placed between the two plates.

There is no free charge in dielectric material. In these material electrons are coupled as dipoles; If dielectric material is placed between the plates:

The potential difference between the plates will decrease.

The charge will increase in each plate.

Capacitor value will increase as an amount of k “dielectric constant”;

0

Ck

C

The potential difference between the plates will decrease as k;

VoV

k

Electric field will also decrease as k value.

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Experimental Setup:

A RC circuit can be built as in the figure below:

Vk:source potential

Vc:capacitor potential

Vr:resistance potential

0

/

; ; .

.

. 0

0 ;

( . ) 0

10 . 0

1. 0

k c R

k R

k

k

k

k

t RCk

V V V

dQ QI V V I R

dt C

QI R V

C

QI R V

C

Vt I

R

d QI R V

dt C

dQ dIR

C dt dt

dQ dI dI dI II R

dt C dt dt dt RC

VI e

R

So as to find the charge difference in time we integrate the current in time (Q0 is the maximum charge value)

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/

0 1 t RCdQI Q Q e

dt

An important parameter for the capacitance is the time constant “τ” (τ=RC)

Apparatus: 1.)Board 2.)Capacitor 3.)DC voltage source 4.)Digital multimeter 5.)Connectors 6.)Stopwatch EXPERIMENTAL SETUP AND MEASUREMENTS: 1.)built the electrical circuit in the figure below.

2.)Apply a potential difference around 1-2 volt to the capacitor.

2.)Close A switch and wait a few minutes so as to charge the capacitor.

3.)Open A switch after it is fully charged.

4.)At the moment you close B switch start the stopwatch and watch how the capacitor is decharging over the resistance. Note the potential difference and the current values on the board.

time(s) Vc(volt) I(A) time(s) Vc(volt) I(A)

1 0 16 200

2 5 17 220

3 10 18 240

4 15 19 260

5 20 20 300

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6 25 21 320

7 30 22 340

8 40 23 360

9 50 24 380

10 60 25 400

11 80 26 450

12 100 27 480

13 120 28 500

14 140 29 540

15 180 30 600

5.)Note the capacitor’s capacitance and the resistance value that you used in experiment.

6.) Note the first current value at t=0.

7.)Compare the capacitor voltage value and the resistance voltage value at t=0 with the applied voltage.

8.)Plot the voltage change during time while capacitor decharge. Find the voltage value where t=τ and compare this value with the calculated τ.

9.)Plot current change during time while capacitor decgharge.

10.)Derive that the capacitor potential change during time while capacitor decharge can be

given by equation /

0

t RCV V e .

11.)

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The current and charge change during time while capacitor charge and decharge characteristics can be given in plots above, respectively. Compare your plots and comment on your results. Find and mark the time where current will decay to its half value in time.

12.) Mark the point where current will take the value of Io/e and then calculate the capacitance value for this specific time point(τ).

13.) Interpret details of the work and make your comment for your measurements and results.

14.)Calculate % Error between the calculated and real values of capacitance.

Further work:

15.)How the capacitance is calculated for the series and paralel connected capacitors?

16.)Define the energy stored on the capacitance.

17.)Define the dielectric materials and explain how they can increase the capacitance of the capacitor in detail.

EXPERIMENT.6

WHEATSTONE BRİDGE:

Goal:1.) Calculating value of an unknown resistance by using Wheatstone Bridge Method

Theory: Wheatstone Bridge is one of the methods that gives absolute result to measure value of a resistance. There are four resistance, a galvanometer, an ampermeter and a power supply in a simple circuit. The value of unknown resistance can be simply measured by getting balance of bridge with the other three known resistance. As the figure below, an unknown Rx resistance and the other three R1,R2,R3 resistance are connected each other. The galvanometer is placed between D and C points. If the total resistance values between parallel branches, the galvanometer don’t read any potential difference. So we can write:

VAD-VAC ve VDB-VBC

With this formula:

I2Rx=I1R1 ve I2R3=I1R2

If we integrate the two formula above we get:

1

3 2

13

2

x

x

R R

R R

RR R

R

If we had conductor metal wire, not a resistance, we would write:

13

2

x

lR

A

lR R

l

Apparatus: 1.)Board 2.)Resistances 3.)DC voltage source 4.)Digital multimeter 5.)Connectors 6.)Galvanometer 7.)Metal wires with various length

EXPERIMENTAL SETUP AND MEASUREMENTS: 1.) Build the electrical circuit in the figure right side. Connect an unknown resistance to place where indicated that Rx . Then apply a voltage nearly 5 V from power supply. Assume that the resistance Rb is rheostat or resistance box. 2.) Observe values on the galvanometer. Change value of rheostat or resistance box until it shows zero. Then record the resistance value that equal to zero of galvanometer. 3.) Calculate Rx from formula using recorded value. 4.) Replace various metal wires with unknown resistance. Determine resistance of wire by changing value of rheostat or resistance box. 5.) Calculate specific resistances of wires that you get their resistance. 6.) Specify kind of metal wires using their specific resistance value. Note: When you measure resistance of wires, the resistances which you use should be low valued resistances. Addition Study: 1.) Explain working principle of galvanometer briefly.

EXPERİMENT 6.

WHEATSTONE BRİDGE:

EXPERIMENT 7.

MAGNETIC FIELD LINES and MAGNETIC FIELD CONCEPT: Goal: 1.) Observing existence of magnetic field, definition of magnetic field lines and magnetization. We will create magnetic field using the methods given below and observe magnetic field lines for each case. EXPERIMENTAL SETUP AND MEASUREMENTS:

1.) by Using a Magnet:

1.) Place a ‘’U Magnet’’ or rod magnet on a white sheet.

2.) Pour iron powder on the sheet and observe magnetic field lines.

3.) Draw your observation on a sheet.

4.) Put the compass to various place around magnet and note direction of compass.

2.) by Using Electromagnet:

1.) Make a simple electromagnet. Coil up conductor wire around an iron screw or a piece of U shaped iron. Form electromagnet by connecting a battery to two edge of the wire. 2.) Pour iron powder on it and observe magnetic field lines.


4.) Put the compass to various place around electromagnet and note direction of compass.

3.) by Using Solenoid:

1.) Connect a battery or power supply to the solenoid as the figure right side and give electric current to solenoid.

2.) Pour iron powder on it and observe magnetic field lines.


4.) Put the compass to various place around solenoid and note direction of compass.

4.) by Using Toroid:

1.) Connect a battery or power supply to the toroid as the figure right side and give electric current to toroid.



4.) Put the compass to various place around toroid and note direction of compass.

5.) by Using simple circuit;

1.) Connect a resistance and conductor wire in series. Then give electric current to the circuit.



4.) Put the compass to various place of circuit and note direction of compass.

Additional Study: 1.) What are the significant points, when drawing magnetic field lines? 2.) Indicate direction of electric field, magnetic field and current for all circuit you built. Explain right-hand rule. 3.) What is the induction? Explain Lenz’s Law briefly. 4.) How can we measure magnetic field’s values that produced by these circuits?

EXPERIMENT 7.

MAGNETIC FIELD LINES and MAGNETIC FIELD CONCEPT:

EXPERIMENT 8.

MAGNETIC INDUCTION: Goal: 1.) Getting some knowledge about Lenz’s Law. 2.) Observing induced current by using Helmholtz coils. EXPERIMENTAL SETUP AND MEASUREMENTS: A simple circuit is built to observe induced current in Helmholtz coils. 1.) Helmholtz coils must be connected each other with banana connectors. 2.) Connect an amperemeter to one of the helmholtz coils.(Scale of amperemeter must read electric current less than mA. Because we want to observe value of induced current instantly.) 3.) Make an electromagnet by coiling up a conductor wire to an iron rod. Then give electric current to the wire.(In some cases, applied current from battery is not enough so you can apply current from DC power supply. In this case, iron rod heats quickly so you must hold the rod with an insulator cloth.) 4.) Did you observe any deviation on amperemeter when you moved electromagnet towards center of coil perpendicularly? 5.) The amperemeter might show very little deviation firstly because of too many loops around coil. Increase current and try again. 6.) Show direction of magnetic field, current and magnetic field lines when you push and pull electromagnet towards center of coils by drawing. Note: If you connect red input of a coil to black input of another coil, magnetic field lines that produced by coils will be in the same direction. If you connect red input of a coil to red input of another or you connect black ones, magnetic field lines that you get will be antiparallel and this case is known as Anti-Helmholtz mode. Magnitude of magnetic field in any Z distance from the center of coils (if the distance between two coils is equal to radius of coils):

2

0

2 2 3/2

1

2 ( )z

N IRB k

z R

7.) Number of loops around coils are written on them. Record the numbers. Then find and note µ0 permeabilty value of free space. Calculate magnitude of magnetic field in any direction for an intended distance. 8.) Interpret your conclusions.

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EXPERIMENT 8.

MAGNETIC INDUCTION:

physics laboratory - ii - marmara...

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