Unit 17Current Electricity

1..

In the above circuit, when the resistance of thevariable resistor is increased,

A the ammeter reading increasesB the voltmeter reading increases

C the ammeter reading decreases

D the readings remain unchanged(

C Both the ammeter and voltmeter would burnout.

D The voltmeter would indicate zero reading.()

4. The figure shows a popular qpe of a rear windowheater consisting of 4 identical heating elements.It operates at72v and carries a current of 4 A.

'12 V d.c. supply

)

2

battery(negligibleinternalresistance)

The resistors P, Qand R in the circuit above haveequal resistance. Ifthe battery is supplying a totalpower of 12 W, what is the power dissipated as

heat in resistor R?

A 2W B 3Wc4w D6W ( )

3. Eugene wishes to find the resistance of a lightbulb. He connects an ammeter and voltmeter as

shown in the diagram below.

What would be the most probable result?A The ammeter would burn out.B The light bulb would burn out.

What are the voltage across and the currentthrough ONE element?

Voltage in volts Current in nmperes1l3483 1

c72 1

D124(

R

)

5. Determine the amount of charge that passes

through a point in a conductor in coulombs if60 mA flow in 10 minutes.436 B 60c167 D600 ( )

6. A cell of e.m.f. 3.0 V passes a current of 1.0 Athrough an external circuit for 1 minute. If thecell has an internal resistance of 0.5 O, how muchenergy is lost from within the cell in joules?430 B60ceo D180 ( )

7. 'Ihe heating element of an electric iron takes a

current of 2.0 A from a 250 V supply. What isthe rate of production of heat in the element inwatts?A 125 B 500c 1000 D 4000 ( )

r\\\\\\\\\\\\r

L\\\\\\\\\\\T

l"

Danya

l Edu

catio

n

8. Which of the lamps in the circuit below has/have

the maximum brightness? (Assume identicallamps are used.)

CV DV

00P

R(

9. The figure below shows a circuit which containstwo identical lamps. When the switch is closed,

which of these statements best describe whathappened to lamps Ll andL2?

L1

L2

A L1 is brighter but L2 does not light up.B L1 does not light up but L2 is brighter than

before.C L1 and L2 are both brighter than before.D L1 andL2 both will not light up. ( )

10. The resistance of wires X and Y are in ratio of2:1 whereas their lengths and diameters are in theratio of 1:2.The ratio of the resistivities ofX:Y is

B 1:2

D 4:7

11. Which one of the following graphs best

represents the voltage-current relationship for a

semiconductor diode?

Ay B v

1.2. 'Ihe effective resistance between terminals P and

Qin the circuit below is c).

o

10()

13. A dry cell of e.m.f. 3.0 V has a wire connectedto its terminals.lf 12 C of charge passes throughthe circuit, what amount of chemical energy is

transformed into electrical energy?

A o.2sl B 3.61c4.0J D35J ( )

1,4. How much work is done in moving an electron

between two points X and Y in the circuit shown

below? (1 e = 1.6 x 10-1e C)

12VX

10e2 10f,

A 1.92 x 10i8JC 3.84 x 10{8 J

B 1.28 x 10{8JD 3.84 x 10-18 J

APC S andT

B Qand PD P andT P

a

AC

15

30820D40

A 1:1

C 2:7

0n

o

10o

0()

r20

()

()

()

()Danya

l Edu

catio

n

15. Two of the wires P, QrR and S are to be connectedto the points X and Y to form a complete circuit.

o

o '4A

S

Ammeter

18. In the circuit, all resistors are identical. If thecurrent at P is 0.50 A, the current from the battery1S

s)2

PR

XY

19. What will happen to the brightness of thelamps P and Qif the resistance of the rheostat isincreased?

]

o

A 0.50 Ac 1.50 A

PA dimmerB dimmerC brighterD brighter

B L.25 AD 2.00 A

P

Which two wires would give the highestammeter reading?A PandQ B QandRC RandS D PandR (

[For Qrestion16 arrd17)

The diagram below show four identical lamps connectedin series with the mains.

4.0 A

240 V mains

16. The voltage marked on the lamp is

-.A 3OV B 6OVc 720v D 240V ( )

20. Which of the following graphs shows therelationship between current I, and voltage V, fora tungsten filament lamp?

A/ B t

a-brighterdimmerdimmerbrighter

n0

C

0

()

D

77. The power rating of the lamp isA 120W B 240Wc 480w D e60w ( )

()

()

I

0

Danya

l Edu

catio

n

21,. A dry-battery will deliver 3000 J of energy to a

small 2-watt electric motor before the batteryis exhausted. The motor will stop running after

minutesA 500c50

22. 'Ihe reading of the ammeter in the first circuit is

3 A. In the second circuit, a resistor of 200 O has

been added.

What is the reading of the ammeter in the second

circuit?

200 a

24. Apiece of steelwire is held between the two clipsin the circuit shown.

rlB 100

D25

23. Wires of various lengths and circular cross-

sectional areas were made of the same material.If the lengths and diameters of the wires were as

shown below, which of these would provide the 26highest resistance?

Length ofwires/cm Diameter/mmA 1.0 2.0

B 2.0 3.0

c 3.0 1.0

D 4.0 2.0()

steel wire

clip

Which of the following changes will make the

bulb dimmer?A Interchanging the positions of the bulb and

the wireB Using a longer length of the same wireC Using a shorter length of the same wireD Using a thicker steel wire of the same length

as the original one ( )

25. the diagram shows two 6 V, 6 W lamps connectedto a72 V battery.

XY

I12V

Which ofthe following statements is NOT correct?

A The ammeter reads 1 A.B The total power dissipated by the lamps is 12 W.C The voltmeter reads 6 V.D If the filament of the lamp Y breaks, the

voltmeter reads zero. ( )

In the circuit diagram shown below, the current fdelivered by the 6 V accumulator will be

6y3 3A

clip

A 3,A.

B slightly less than 3 AC slightly more than 3 AD about3OOA (

A less that2 AC more than 2 A

B 2AD infinitely large

()

()

20

r22

Danya

l Edu

catio

n

27. What is the value of R if voltmeter V read 4 V?

10v

5A R

28. In the diagram below, what are the readings of thevoltmeter V and the ammeter A?

The filament of one of the bulbs breaks. Whathappens to the ammeter reading and to thebrightness of the remaining bulbs?

Ammeterreading BulbbrightnessA increases increasesB unchanged unchangedC decreases unchangedD decreases decreases

()

31. Three resistors of resistance 1 A, 2 O and 3 Orespectively are used to make the combinations X,Y andZ shown in the diagrams.

43.c6.

3C)0C)

1O

ReadinginAA 2.OAB 2.OAC 3.OAD 3.OA

A 2.0ac 4.0a

2A

ReadinginV2.0v4.0 v2.0v4.0v

B 5.0c)D 7.5A

B 1.3 C)

D L2A

6.0 v

29. the equivalent resistance between Y and Z is

x silver plate

2.0

2.0 ()

X2A 2A

1eJ

z3O

Which of the following gives the combinationsin order ofincreasing resistance?AWZ B XZYc\xz DZw ( )

lA

What physical quantity is described by thegradient ofthe graph?A resistance

B 1/resistanceC work done by the chargeD power ( )

O

VN32

(

30. Three similar light bulbs are connected to a

constant-voltage d.c. supply as shown in thediagram. Each bulb operates at normal brightnessand the ammeter (of negligible resistance)registers a steady current.

1A 3A

1c, 2A

()

I

()

I

3s2

Danya

l Edu

catio

n

33. Which diagram shows the I/V characteristic

graph for a conductor that obeys Ohm's Law?

A/ B t

0

Ct

37 . -Ihree 10 C) resistors were connected in a circuit as

shown in the diagram below. What is the currentflowing through resistor P?

10v

+

10(2

10(2

P

A 0.20 Ac 0.67 A

Lamp 1

A brighterB brighterC brighterD dimmer

Lamp2brighter

stays same

dimmerbrighter )

()

0

D

U 0

34. When a p.d. of 2 Y is applied across a resistor,10 J of energy are converted. What charge flows

through the resistor?

A 0.20c B 5.0Cc72C D2oC ( )

35. In the circuit below, the voltmeter reading is

1.5 V and the ammeter reading is 0.30 A. If theresistance of the ammeter is 1.0 C), what is theresistance R?

1.5 V

R 0.3 A

B 5.0 C)

D 7.0 C)

38. Which two ammeters in the diagram below have

the same reading?

B 0.33 AD 1.OA

A 4.00c 6.00 ()

36. The diagram shows a potential divider circuit.

L.t

What happens to the brightness of lamp 1 and

lamp 2 as the contact X is moved towards end P

of the potential divider?

B A, and A,D A, and Au

A A, and A,C A., and A,

L2

)

10o

()

I

I

124

Danya

l Edu

catio

n

39. Which of the following graphs correctly showsthe relationship between the resistance R of a

wire and its cross-secti ond, area,l[?

A ata B R/a

A/cm2 A/cm2

D R/a

A/cmz A/cm2

40. When a current of 2 A flows for 5 s through a

lamp,720J of energy are transformed. How muchcharge flows through the lamp?A 1OC B 1,2Cc24C D60C ( )

47. 'Ihe diagram below shows a circuit connected by astudent who intends to control the brightness ofabulb. Which of the statements below is correct?

A The bulb becomes brighterwhen the rheostat isadjusted to a higher resistance because it allowsmore current to flow through the bulb.

B The bulb becomes dimmer when the rheostatis adjusted to a bigger resistance because itreduces the potential difference across the bulb.

C The brightness ofthe bulb cannot be adjustedbecause the potential difference across the bulbis constant.

D The brightness ofthe bulb cannot be adjustedbecause its resistance is always constant.

()

42. the resistance of a wire is R and its length andcross-sectional area are L and,,4 respectively.When its length is increased to 3L and its cross-sectional area to 2t{,what is its resistance in termsof R?

e.?n B 1p3 - 2--c2R D3R ( )

43. What is the reading on the voltmeter in thepotential divider circuit below?

100 v

100 ka

300 ko

OV

44. Aland Arare two ammeters of negligible internalresistance. What will happen to the readings ofthe ammeters if the switch S is closed?

A 25VC 5OV

ReadinginA,A No change

B Decreases

C No change

D Decreases

B 33VD 1OOV

ReadinginA,Increases

Increases

Decreases

Decreases

45. What is the potential difference across the cell?

t0A 20a

4.0 A

B 220VD 6OV

45. 'Ihe unit volt isA a flow of one coulomb of charges per secondB a dissipation ofenergy ofonejoule in 1 secondC a dissipation ofenergy ofonejoule per unit

ampere of current fowD a dissipation ofenergy ofonejoule per unit

coulomb of charge flow ( )

VV

4401.20

AC

30o

C AK)

()

()

()

()Danya

l Edu

catio

n