142 lheme 5 I Electricity oncl Mognetism

l Current of Electric itvond D.C. Circuits

For each ol the questions, there are four possible choices.Ghoose the one you consider collect and record your choice.

\\,0r What is electrical current?

A Rate of change of voltage.B Rate of change of resistanceC Hate of flow of charge.

D Rate of flow of power.

U 2. What does 5 A refer to?

A 5 C of charge flows through a point in 1 second.

B 5 V of electricity across 1 Q of resistance.

C 5 V of electricity causing 1C of charge to f low.

D 5 C of charge flowing through a point. (

M0 3. Which of the following is true about point P?

6V3A

2A

A Current is flowing in direction 4.

B Electron is flowing in direction 4.

C Electron is flowing in either direction 1 or direction 3

D Electron is flowing in direction 2. (

Mg 4. Which ls a unit of current?

AOV B

C Cs-1 D

Ms 5. How much charge flows through the

resistorBin4s?6V

B 6CD 18 C

1. A cell containing 1200 C of charge is connected to a circuit.What is the time taken to discharge the cell given that thecurrent in the circuit is 6 A?

A 0.005 h B 200 hC 200s D 7200s (

)

B. 100 C of charge is stored in a cell. Given that 50% of thecharge flows out of the cell in 10 s, what is the average rate

of flow of charge out of the cell?

A 0.1 A B O.5Ac 5A D 10A (

)

9. The p.d. across a resistor is 12 V How much energy is grven

out by the resistor when 3 C of charge flows through theresistor?

A 0.25J B 2JC4J D36J ()

10. 3 J of energy is disslpated from a circuit when 6 C of charge

flows through the cell. What is the e.m.f. of the cell?

A 0.5V B 2Uc 4v D 1BV ( )

11. The circuit below is switched on for 30 seconds. Calculate

the amount of energy dissipated by the 3 Q resistor.

6V

3A

M0

U

VR

CV

d

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W

W

B 180 J

D 54OJ

12. Ihe circuit below is switched onfor 2 minutes. Calculate theamount of energy dissipated by resistor B

l0v

J

A

C

60J360

AC

C3

12C 2

6. lf 50 C of charge flows through a point in an electric circuit

in 10 s, what is the current passing through that p0rnt?

A O.2A B 5Ac 60A D 500A ( )

a

A 16JC 960J

B 40JD 2400 J

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13. What is an electromotive force?

A lt is the work done by an appliance in driving electronsround a circuit.

B lt is the work done by a source in driving a unit chargeround a circuit.

C lt is the work done to drive a unit charge through a

component.D lt is the product of current and resistance. ( )

14. lf the e.m.f. of each cell is 1.5 V what is the voltage acrossthe resistor fl

Unit l7 I Current of Electricity cnd D.C. Circuiis 143\Vs 18. lf the e.m.f. of the cell in the circuit shown below is 12 V

what is the current in the circuit?

t2v

15. What is the resistance of the resistor in the circuit shownbelow?

6V3A

R

B 44D 124

19. lf a current of 4 A flows in the circuit shown below, what isthe resistance of the resistor B?

20v

3A

21. ln the circuit below, how much charge passes through the2 e) resistor in a minute?

12Y

AC

3A6A

rlrlrl W

v

^

A 1.5VC 6V

B 4.5VD 12V

R

20. What is the e.m.f. of the cell in the circuit shown below?

\Vg

t\,g

AC

sJ

O0

OO

2

5

5V9V

3

1

D

D

A O.3V

C 4VB 3VD 12V

U,r. *nu, is the e.m.f. of the cell in the circuit shown below?

A 0.5ac 3e2

B 2(2D 18O

16. What is the voltage across the 2 Q resistor in the circuitshown below?

A

22. lf 720 C of charge flows through the 2 el resistor in 6 minutes,

what is the e.m.f. of the cell?

A

C

3V6V

4C240

A

DU

D

N

C

B 6CD 360C

W

A 1.5Vc 12V

A

C

2VbV

2A

Io

6A

B 3VD 24V

B 4VD 12V

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144 Theme 5 I Electricity ond Alogne'tism

23. What is the potential difference across the 1 Q resistor and

the 3 Q resistor in the circuit shown below?

p.d. across

3 Q resistorA 1.5VB 2VC 1.5VD 6V

o.d. across1 Q resistor

1.5 V

6V4.5 V

6V

U

d

d

A 3Oc 12A

24. What is the potential difference across the 2 Q resistor in

the circuit shown below?

6V

25. What is the effective resistance of the three resistors in thecircuit shown below?

B 3AD 24A

26. What is the effective resistance of the two resistors in thecircuit shown below?

27. What is the effective resistance of the two resistors in thecircuit shown below?

28. What is the effective resistance of the three resistors in thecircuit shown below?

A O.3OC 3O

B 1.1 OD 12A

29. What is the effective resistance of the four resistors in thecircuit shown below?

tV0

AC

2

1l

B

D

oa

eJ5

a0o

\Vs

\V0

1

6

AC

2V12V

B

D

A 0.25 AC 6e2

B 4e2D lBO

U

A 1Ac 9a

30. What is the effective resistance of the three resistors in thecircuit shown below?

A O.4Oc 11A

31. What is the effective resistance of the four resistors in theclrcuit shown below?

B B.OOD 33O

B 4e2D 13O

v

A

C

5 aa

3O

3f) 9O

2Q 3Q 4C'

6O

3f) t2QB 6()D 36O

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U rr. *nr, is the current that flows through the 3 Q resistor?

Unit 17 I Curr*nt rsl Electrictly and D"C. Circuits 145tVS :2. Wf,at is the potential difference across the 3 Sl resistor?

6V

6V

12v

2.BVBV

A

C

B

D

4

U rr. *nu, is the current that flows through the 1 Q resistor?

12V

38. A 2 m long wire has a resistance of 16 Q. What is theresistance of this wire if it is 1 m long?

A 4A B 8s2c 32a D 64() ( )

39. A 2 m long wire with a cross-sectional area of 1 mm2 has aresistance of 16 a. What is the resistance of the wire if ithas a cross-sectional area of 2mmz?

A 4s) B BOc32A D64O (

)

40. Wire A has a resistance of 16 A. Wire B has the samedimensions as A but is made from a material which has halfthe resistivity of wire A. What is the resistance of wire B?

A 4f) B BOc 32a D 64() (

)

41. A2 m long wire with a cross-sectionalarea of 1 mm2 has a

resistance of 16 Q. What is the resistance of the same typeof wire which is 4 m long and has a cross-sectional area of2mmz?

A 4AC 16O

42. A2 m long wire with a radrus of 1 mm has a resistance of16 A. What is the resistance of the same type of wire whichis 4 m long and has a radius of 2 mm?

A 4e2 B BOc16o D32o (

)

43. A I m long wire with a diameter of 3 mm has a resistanceof 16 Q. What is the resistance of the same type of wirewhich is 2 m long and has a diameter of 2 mm?

A 2.7A B 3.6e)c 6e, D 9e, ( )

44. Wire A and wire B have the following ratios

lengthlo _ 5 . diameter4 _ 2. resistivitypo _ 4length l, 18' diameter D, 3' resistivity p, - g'

What is the rati0 0f the resistance of wire A to the resistanceof wire B?

A 5:18 B 10:54C 18:5 D 54:10 (

)

A 1.5AC 6A

A 1.5AC 6A

A

C

1.5 A

6A

B 2AD BA

B 2AD BA

B

D

2ABA

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v

v

U rO. *nu, is the current that flows through the 6 V cell?

IVgB BAD 32A35. What is the potential difference across the 2 S) resistor?

12Y

36. What is the potential difference across the 4 e resistor?

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2

6

A

C

B

D

Mg

4V12U

4V12V

B

D

A 3.7VC 8V

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146 Theme 5 I Flectricity ond Alogneiism

Wou. *,r. A and wire B have the following ratios.

resistivity p,

resistivity pB

U

v

rncrease

i ncrease

decrease

decrease

v

Given that wire B is 2 Q, what is the resistance of wire A?

A 0.170 B 4e2c 6s, D 12a ( )

46. What is the use of the variable resistor rn the crrcuit in the0hm's law experiment shown below?

1. To change the voltage across the fixed resistor.

2. To change the resistance across the fixed resistor.

3. To change the current flowing through the fixed resistor.

A lonly B 3onlyC land3only D 1,2and3 ( )

4l . ln the circuit diagram, what will happen to the readings on

the voltmeter and the ammeter if the variable resistance is

i ncreased?

Voltmeter readlng Ammeter reading

49. As the temperature of a metallic conductor increases,

A its resistance increases because the ions in the conductor

expand making them more likely to obstruct and slowdown the flow of electrons.

B its resistance increases because the ions in the conductorvibrate with bigger amplitude, making them more likelyto obstruct and slow down the flow of electrons.

C its resistance decreases because the ions in theconductor expand making them more likely to obstructand slow down the flow of electrons.

D its resistance decreases because the i0ns in theconductor vibrate with bigger amplitude, making themmore likely to obstruct and slow down the flow ofelectrons. ( )

50. Which of the f0llowing is a possrble explanation for thefollowrng 7-lgraph of a tungsten wire in a Iight bulb?

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uA

A As the voltage increases, the current flowing throughthe tungsten wire is increased proportionally accordingto Ohm's law.

B As current increases, the temperature increases and

therefore the resistance of the tungsten wire in the lightbulb increases.

C As current increases, the temperature increases and

therefore the resistance of the tungsten wire in the lightbulb decreases.

D As current increases, the temperature increases and

therefore the charges f lowing through the tungsten wirein the light bulb increase. (

)

51. ln the circuit below, the lamp brightens up as the rheostatis being adjusted.

length l,length l,

diameter 4diameter D,

4

3

2

3

2

1

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v

0

r ncrease

decreaselncrease

decrease

48. The t/-/ graph of a wire is given below. What is the reslstance

of the wire al V =2 V and t/= 10 V?

tangent=44,

atl

IIA

ABr-

D

l0

6

4

2

1234

Resistance at 2 V

A O.5OB O.5OczaD2A

Resistance a1 10 V

0.4 a0.2 a2.5A6O

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Which of the following graphs best shows how the ammeterreading /varies with the voltmeter reading 14

UnitlT I Current olElectricity and D.C. Circuits 147

Resistor 1 and resistor 2 are connected in parallel. Thepotential difference across resistor 1 is 12 V What is thecurrent following through the cell?

A 34 B 64c 9A D 1BA ( )

W 54. The l-Vgraph of a resistor 1 and resistor 2 is shown below.

.""! '/1e,/

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BV

0

CY

0

DV

0

v

l0

9

8

7

6

5

4

3

2

1

0

l0

9

8

7

6

5

4

J

2

I

0

M0 SZ. tne LVgraphof a resistor 1 and resistor 2 is shown below.

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l0

9

8

1

6

5

4

3

2

I

0

t0

9

8

7

6

5

4

.,

2

1

0

ilA

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Z

Resistor 1 and resistor 2 are connected in parallel. Thepotential difference across resistor 2 is 20 V What is theeffective resistance of the circuit?

A 1.3O B 2.OOc 4.0o D 6.0e) (

)

55. The t/Jgraph of a resistor 1 and resistor 2 is shown below.

.rol /{ ,/

*.t

Z

2 4 6 8 tOt2 14t6 1820 vlv

2 4 6 8 r0 12 t4 t6 l8 20 t/A

Besistor 1 and resistor 2 are connected in series. The currentflowing through the circuit is 5 A. What is the e.m.f. of thecell?

A 1OV B 2OV

c 30v D 60v ( )

53. The l-Vgraph of resistor 1 and resistor 2 is shown below.

IIA

..ait/

1( "/-.01

Z

2 4 6 8 r0 t2 14 t6 18 20 Vlv

2 4 6 8 t012t4t6 1820 vtv

Besistor 1 and resistor 2 are connected in series. The powerdissipated from resistor 1 is B W. Calculate the powerdissipated by the cell 0f the circuit.

A 12WC 18W

B 16WD 24W

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148 Theme 5 I Flectricity ond Mognetism

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0 SO. Which item will produce the ltlgraph shown below?

A filament lampC semiconductor diode

v/v

B fluorescent tubeD thermistor

d

d

d

51. Which of the following will produce the lllgraph shownbelow?

IIA

0

A filament lampB fluorescent tubeC semiconductor diodeD ideal semiconductor diode

58. Point P is a point along a wire. What is the current /?

2A P I

A -24C 1A

B

D

59 Point P rs a junction in a circuit. What is the current /?

24, P I

3A

OALt\

B _1 AD 5A

N,U OO. Point P is a junction in a circuit. What is the current i?

A -5AC 1A

A _1 AC 1A

6A

P I

0DU

D

A

24,

3A

11A

2A,

d

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61. A 1 2 V cell is connected t0 three resistors arranged in series.What is the voltage across resistor E?

12Y

2v 4V

OV6V

AC

2V5V

A

C

2tr

2B

D 12V

62. 412 V cell is connected t0 two resistors arranged in seriesWhat is the voltage across resistor B?

t2v

10v

63. A l2Vcell isconnectedtothree resistorsarranged inseries.What is the voltage across resistor B?

12V

2V

64. lf the ammeter reading is 2 A and the voltmeter reading is

5 V what is the e.m.f. of the cell in the circuit?

cell

B

D

4

A

A

C

4V6V

B

D

v

A lOVC 20V

15

25

B

D

tu6V

B

D

1V5V

AC

U uu. *nu* is the voltage across the 1 Q resistor?

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W UU. *n., is the current flowing through the cell?

2A

B 64D 12A

V Ur. *nu, is the current flowing through the resistor B?

AC

2ABA

3A6A

A

C

2A

2A

24v

B

D

4A9A

V uu. *nu, is the resistance of resistor B?

B 4()D 12A

69. A 10 Q resistance wire AB is connected in a circuit as shown.

Given that the resistance wire is 2 m long, what is the reading

on the voltmeter when the jockey is at point C?

12V

. l.6mA+------ -----------) B

B 24VD 12V

A2Ac 6A

U

An

1.6 V

9.6 V

6s2

Unit I7 I C*rent cst trle clric.ily rsnd D.C. Ctcuils 149M0 70. A 10 el resistance wire AB is connected in a circuit as shown.

Given thatthe resistance wire is 2 m long, what is the readingon the voltmeter when the jockey is at p0int C?

t2Y

t.5 mA+- -- -- -- -- -- -- -- >

A 2,5VC 7.5V

B 6.0VD 1OV

v

v

11. 412 Q resistance wire AB is connected in a circuit as

shown. Given that the reading of the voltmeter is 0 V whenthe jockey is at the positi0n shown, what is the resistance

of the resistor F?

1.6 m

B 6AD 10A

72. A resistance wire AB is connected in a circuit as shown.What happens to the brightness of the lamps as the jockey

slides along the resistance wire from point A to point B?

lamp P lamp Q

A Lamp P gets brighter while lamp 0 gets dimmer.B Lamp 0 gets brighter while lamp P gets dimmer.C There is no change in the brightness of lamp P and lamp

0.D Both lamp P and lamp 0 do not light up. ( )

+------------A

A 4AC BO

A

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150 Theme 5 I Eleclricity ond Arlognetisnr

73. A 3 V cell is connected across two uniform resistance wiresAB and CD of resistance 2 Q and 1 Q respectively. Length

of AB is 3 cm and length of CD is 6 cm.

3V

\\,g

v

A VIY B v/v

4

Llcm

6

4

2

DvABCJD C v6

JD

lcm

Llcm

lcm

t23456

t23456

4

2 2A voltmeter with a point fixed at A and the other end

connected to a jockey slides from point C t0 point D. Whichof the following diagrams shows the voltmeter readings as

the jockey moves? (l is the length from C to J)

A VIY B VIY

t23456

ABC

t23456jLlcm

L

3

0

C VIY3

v

0

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6

75. A 6 V cell is connected across two uniform resistance wiresAB and CD of resistance 2 Q and 1 Q respectively. Length

of AB is 3 cm and Iength of CD is 6 cm. The connecting wireBC is 1 cm. (L is the length from C to J)

6V/cm

L lcm

Dv

Llcm

Llcm5

ABC

A voltmeter with a point fixed at the mid-point 0f AB and theother end connected to a jockey slides from point B to point

D. Which of the following diagrams shows the voltmeterreadings as the jockey moves?

74. A 6 V cell is connected across two uniform resistance wiresAB and CD of resistance 2 Q and 1 Q respectively. Length

of AB is 3 cm and length of CD is 6 cm. (l is the length fromCtoJ)

6V

Av6

4 1

Bv6

2 2

0 l23456lLlcrn

CV6JD1

22

0A voltmeter with a point fixed at the mid-point of AB and theother end connected to a jockey slides from point C to point

D. Which of the f0llowing diagrams shows the voltmeterreadings as the jockey moves?

4562 /cm 7

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W 76. A 6 V cell is connected across two uniform resistance wiresAB and CD of resistance 2 Q and 1 Q respectively. Length

of AB is 3 cm and length of CD is 6 cm. The connecting wireBC is 1 cm. (l is the length from C to J)

6V

ABC

u

JD

A voltmeter with a point fixed at A and the other end

connected to a jockey slides from point A to point D. Whichof the f0llowing diagrams shows the voltmeter readings as

the jockey moves?

Av Bv

3

C vtv

cnrL

v

cm

D

L

6 65I3

1

3456789r0 /cm

For question 17 lo 81, the resistance of the thermistordecreases with increasing temperature, and the resistanceof the light dependent resistor decreases with increasingtemperature.

cml0

U rr. ,n. lamp in the circuit below will light up

A on a hot day.

C under bright light.B on a cold day.

D in a dark room. (

Urr. ,n. lamp in the circuit below will light up

A on a hot day. B on a cold day.

A 1A B 2A

Unit I7 I Current al Cl*ctricily and D.C. Circuils 1 51

C under bright light. D in a dark room. ( )

U rn. ,n. lamp in the circuit below will light up

AonCun

a hot day.

der bright light.

A on a hot day.

C under bright light.

A hot and bright.C cold and bright.

+

B on a cold day.

D in a dark room

+

B on a cold day.

D in a dark room

B hot and dark.D cold and dark.

V rO. ,n. lamp in the circuit below will light up

\

N1iU et. the lamp in the circuit below will light up when it is

v 82. Calculate the resistance B.

36V6A

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6e2

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152 Theme 5 I Electricil.y c:nri A4cgnetism

83. Calculate the current which flows through the 4 O resistor

48V

v 84. Calculate the resistance B.

36V6A

A 1A B2AD 12Ac 3A

U

\\,S gS. Calculate the effective resistance of the circuit below.

AC

B

D

1

JAA

2A4A

W gO. Cutrrtate the effective resistance of the circuit below.

A 4Ac 24A

B 12OD 36e2

B 12AD 36O

12Q6Q t2a

6O1.) 6e)

4o

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EXTENSION QUESTIONS

1,2Q t2a 12c)

t2a l2Q 12o

A4AC 18O

A 2AC 18O

B 6e2D 12A

20c,

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87. What is the effective resistance of the nine resistors?

20c)

O

A 5eJc 15A

B 10AD 20O

BB. Calculate the effective resistance between the points Xand Y.

x

10

Y

W gg. Cutrrtate the effective resistance of the circuit below

A 1.5Oc 60e)

A 0.67 OC 6.0O

B 4.OOD 1OB O

B 1.5(2D 60O

V gO. Cutrrtate the effective resistance of the circuit below.

t2a

12s)- 6O 6O

t2a

12e]-

12e2

12o 12o

12o t2at2Q

t2a

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V gt. Cutrrtate the effective resistance of the circuit below.

Unit l7 I Current rsf trlec}ricily csnd D"C. Cucuits 153

U nU. *nr, is the voltmeter reading in the circuit below?

\Vg

A2UC 20V

B 18VD 22V

M0 97. What is the value of current /, in the following circuit?

2V20v

B

D

96. What is the voltmeter reading in the circuit below?

0

5

A

CA 764Ac 36.0 s2

B 27.0AD B4.O O

v 92. Calculate the effective resistance between the points Xand Y

x Y

A 6e2c 24A

B 12OD 36O

d "

What is the voltmeter reading in the circuit below?

6V

t2

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2dt3Il

B

D

31A4A

A

C

3

6

B

D

A

124

1V6V

B

D

94. What is the voltmeter reading in the circuit below?

OV

5VA

C

0

5

AC U nr. *nr, is the value of current i, in the following circuit?

d

I1

A 1AC 4A

A

A

IQ

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3c)

B2UD 20V

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3s24Q 2A

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154 Theme 5 I Electricity cnd Mognetism

W rr. *nu, is the value of current /, in the following circuit?

2A

12v

A 4 only

C 2,3 and 4 only

B 3and4onlyD 1,2 and 3 only (

4 2{)

ll

2

B 1.5AD 3.OA

100. Which of the following is the waveform for direct current?

e.m.f. e.m.f.

e.m.f e.m.f.

AC

1.0 A2.0 A

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2

time

43

W 101. A resistor can be added to the clrcuit below to make thecurrent /= 3A. Which is it?

t2v

B 4f2D BO

'102. A resistor can be added to the circuit below to make thecurrent /= 34. Which is it?

t2Y

2

6

An

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2{) 4e)

A2Ac 10a

B 6s2D 12A

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103. The circuit diagram shows four identical resistors connectedin series with a battery. What are the possible readings on

voltmeters V, and V,?

v2'1 \/

8V6V6V

1 04. A student wants t0 know the resistance of a conductor whena current /= 0.50 A flows through it. How can he obtain theresu lt?

A By calculating the gradient of a [/-/graph.B By calculating the gradient of a I l/graph.C By calculating the gradient of a [/-/graph at /= 0.50 A.

D 0btainthecorresponding p.d. l/acrosstheconductorwhen

/= 0.b0 A. Then calculate resistance using ffi()

t\,0 t OS. Which of the following statements is correct?

A

B

C

D

v1

1V2V3V4V

AlzB/3CI,D4

I2

U ,l ou what is the value of current I

= ltand l,= lz+

is smaller thanis greater thanis greater than

t2A

l3

/, but bigger than l./, but smaller than (./, but smaller than /,.

A

C

3A6A

B 4AD BA

lc)

20

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v 107. ln the figure below, AB is a 2 m long resistance wire. WhenAC = 1.6 m, the galvanometer indicates a zero reading.

1.6 m

Unit 17 I Cr,rrrent of Electricitv and D.C. Ctcuits 155Ms 1 10. What happens to the brightness of the lamp when the switch

is closed?

becomes dimmer.becomes brighter.goes off.remains the same.

M0 111. Six 6 Q resistors are connected to a 6 V cell of negligible

internal resistance as shown below. What is the current thatflows through point P?

+------------)A C

AltBltCltDlt

\V0

U

What is the resistance of B?

A 6s) B 12Ac 24A D 30eJ

108. Three resistors, each of resistance 6 Q, are arranged to give

a 9 Q combination across P0. Which of the following is thearrangement?

A

PP

I A 0.17 Ac 0.67 A

B 0.33 A

D 1.00 A

B 0.25 AD 1.25 A

P

vC

1 1 2. Five 6 Q resistors are connected to a 6 V cell of negligibleinternal resistance as shown below. What is the current thatflows through point P?

P

D

PP

AA

0.20

0.50

A

C109. ln an experiment, four resistance wires made from the samematerial are connected in turn between the terminals P and

0 in the circuit shown. The length and diameter of the wiresare different.

PQ

Which wire will give the smallest reading on the ammeter?

Length DiameterA 0.5 m 0.5 mmB 0.5 m 0.05 mmC 5.0 m 0.5 mmD 5.0m 0.05mm ( )

U , ,1,

Calculate the value of current / in the diagram below

A 1.3AC 4.OA

B

D

2.0

6.0

AA

6 6O

€

o

6O

6O 6f)

6()

6O

12V

B

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()

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()

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()

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156 Theme 5 I Electricity cnd Ilognetism

U , , o. Calculate the value of current / in the diagram below 118. Which of the following graphs shows the relationshipbetween the resistance Bof a wire, and its cross-sectionalarea A?

A R/a B nlo

Al mm2 Almm)

C R/a D nlo

Almml Almm)

(

119. Which of the following statements is correct for the circuitshown below?

A The bulb becomes brighter when the rheostat is adj usted

to a higher resistance because as the resistanceincreases, the potential difference increases.

B The bulb becomes dimmerwhen the rheostat is adjustedto a higher resistance because as the resistancedecreases, the potential difference decreases.

C The brightness of the bulb cannot be adjusted because

the potential difference across the bulb is constant.

D The bulb will fuse when the rheostat is adjusted to 0 Q()

120. A circuit is connected as shown in the diagram. Given thatthe three resistors are identical, which of the followingstatements are true?

1. Ao has the highest reading.

2. A1, A2and A, have the same reading.

3. Beading of Au is greater than Au.

A 1.OAC 3.OA

1 15. Calculate the value of current / in the diagram below.

12Y

B

D

AA

2.04.0

82,D4.

\\,g

M0

v

A 1.OA

C 3.OAOAOA \

U ', ',U. ln the circuit shown below, the ammeter reads 0.50 A whenS, is closed andreading be if both

s2

s1

is opened. What would the ammeterand S, are closed?

6V

s1

UA 0,67 A

c 1.33 A

B 0.75 A

D 3.00 A

\\,g1 17. ln the circuit below, lamp P has twice the resistance of lamp

0. The relationship between the current { and current ( is

P

A

C

B 2t =to 1'= +{

=t,2f,

4l0

t=p B l and3only

D 1,2and3

6e2

A l and2onlyC 2and3only

I

I

( )

)

I

)

(

)(

()()

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W

121. Given that the resistance of the LDB decreases withincreasing brightness, how do the voltmeter readings changeas the surrounding gets brighter?

Unit l7 I Currenl al Lleclricily rsnd D.C" Circuits 157

P

R

S

\\I A lamp P becomes dimmer.B lamp P is as bright as lamp 0.C lamp P is not as bright as lamp B.

D lamp P remains as bright as when switch S is opened.()

V',ru. Bulb 1 and bulb 2 are connected in series as shown below.

AB

C

D

decreasesremains unchanged

i ncreases

increases

rytQJ6

4

U

.V,r ncreases

decreases

increases

decreases

122. Besistors R,and Rrare connected in a circuit as shown below.When switch S is opened, the ammeter reads 1.5 A and thevoltmeter reads I V. When switch S is closed, the ammeterreads 3.0 A and the voltmeter reads 6 V.

What are the resistances of B,and Rr?

S

bulb I bulb 2

What will happen to the brightness of the two bulbs whena third identical bulb is connected across light bulb 1?

bulb I bulb 2

A

B

C

D

Brl Qb

3

B

4

Bulb 1

A brighterB brighterC dimmerD dimmer

Bulb 2

brighterdimmerdimmerbrighter

V ',rr. The circuit below contains two perfect ammeters

When the swrtch is opened, the reading of A, is I Whenthe switched is closed, the reading of A, is I Calculate theralio of 1,. lr.

v

24. ln the circuit below, the three lamps are identical. Whenswitch S is closed,

1 26. A heater a fan and a bulb are connected to the 1 2 V batteryas shown in the diagram.

12v

IAheater

The fan with a resistance of B has a p.d. of 6 V across itand a current of 1 A through it. The bulb has a current of2 A flowing through it. Which of the following is true?

A The voltage across the bulb is 6 V and its resistance is2R.

B The voltage across the bulb is 6 V and its resistance is1^in.

fan

A 2.1C 4:3

B 3.2D 5:2

(

(

bulb2A

U,

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158 Theme 5 I Electricity ond Mcgnetism

12l.Iwo wires P and 0, each of the same length and the same

material are connected in parallelto a cell. The diameter ofP is half the diameter of 0. What fraction of the total currentpasses through P?

131 . From the diagram below, what are the potential at point 1,

point 2, point 3 and point 4 respectively?

t2v

lkQ

2kc)

OV

v

tVSr

U

A B n1"zC+J

v

v

W

2

4V8V4V4V

2

4V4VBVBV

4VBVOV12U

.)J

OV

OV12V12V

4

8V4VOV12U

4

OV

12U12UOV

5 4

V',rt. Four resistors are connected as shown in the diagram

P

6 6OAB

C

D

BV4VBVBV

8V8V4V4V

A

B

D

Which two points when connected to terminals X and Y in

the following circuit will give the highest reading on the

ammeter?132. From the diagram below, what are the potential at point 1

point 2, point 3 and point 4 respectlvely?

t2v

lkQ

I

2ko

OV

XY

and 0and 0

and

29. A heater produces 2.4 kW when a 240 V mains supply is

connected across it. What is the resistance of the heater?

A 10O B 24Ac 120e, D 600e2 ( )

130. 0ne of the four identical light bulbs in a series circuit has

blown off as shown. What will be the voltage readings (and Vr?.

t2v

open circuit

133. Calculate the resistance B of the three identical resistors

shown in the circuit below.

6V

BODS

APCB and

c

P

B 2s)D 4A

A 1OC 3e2vl lv

A OV

B 3VC OV

D 3V

v2

0

3V12UOV

lko

2ko

lkQ

2ko

3

rkc)

1 kc2

I

2 kc,

lkQ

2

2ko

3

lko

()

()

()

()

()

()

2kt)

1

2ko

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W',r0. What is the resistance of the resistor labelled E?

Unil l7 I Cwr*nt af Ylect*cily {.}nt) D"C.. Circ,,tils 159Given that the ammeter reading and voltmeter reading are0.20 A and 1 .20 V respectively, what is the new reading whenanother identical resistor is attached as shown below?

B 4eiD BA

A2AC 6e)

AmmeterA 0.10 AB 0.10 A

c 0.20 A

D 0.20 A

Voltmeter1.20V2 40V1.20V2.40V

W',ru. Calculate the current I5O U

29

A 1AC 34

36. A cell, an ammeter, a voltmeter and a resistor are connectedas shown below.

Given that the ammeter reading and voltmeter reading are0.20 A and 1.20 V respectively, what is the new reading whenanother identical resistor is attached as shown below?

138. A cell, an ammeter, a voltmeter and a resistor are connectedas shown below.

Given that the ammeter reading and voltmeter reading are0.20 A and 1 .20 V respectively, what is the new reading whenanother identical resistor is attached as shown below?

2 2

80v2

B

D

2A4A

IVSr

AmmeterA 0.10 AB 0.10 A

c 0.20 AD 0.20 A

Voltmeter0.60 v1.20 V

0.60 v1.20V

AmmeterA 0.20 AB 0.20 Ac 0.40 AD 0.40 A

Voltmeter1.20V2.40V1.20U2.40V

37. A cell, an ammeter, a voltmeter and a resistor are connectedas shown below.

5A

5()

5

5

A

V

A

V

A

V

A

V

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