Electrical Quantities (Cambridge O Level Physics)

Exam Questions

3 hours45 questions
1a
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4 marks

A student sets up an electrical circuit. She draws part of the circuit diagram, as shown in Fig.8.1.

feb-march-2018-32-q8

On Fig.8.1, draw the circuit symbols for three devices so that the student can:

 
(i)
measure the total current in the circuit
[1]
 
(ii)
vary the current in the lamp B only
[1]
 
(iii)
measure the potential difference (p.d.) across lamp B.
[2]
1b
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3 marks

The current in lamp A is 0.20 A. The potential difference (p.d.) across lamp A is 6.0 V.

 
Calculate the resistance of lamp A.

 

resistance = ......................................................Ω 

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2a
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5 marks

Fig. 9.1 shows a simple circuit.

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(i)
The current in the wires of the circuit is a flow of particles.
Indicate the name of these particles. Tick one box.
 

      square electrons

      square atoms

      square protons

[1]

(ii)
Calculate the combined resistance of the two resistors.
 
resistance = ...................................................... Ω [1]
 
(iii)
Calculate the potential difference (p.d.) reading that would be shown on the voltmeter.
 
potential difference (p.d.) = ...................................................... V [3]

2b
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2 marks

The circuit is changed.

The two resistors are connected in parallel.

 

Explain what happens, if anything, to the current reading on the ammeter.

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3a
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3 marks

Fig. 10.1 shows a balloon hanging from an insulating thread.

q10a

(i)
A student gives the balloon a positive charge.
 
   Which statement explains why the balloon becomes positively charged? Tick one box.
 
 square The balloon gains electrons
square The balloon loses electrons
square The balloon gains protons
square The balloon loses protons

[1]

(ii)
The student brings a charged rod close to the balloon as shown in Fig. 10.2.
q10aii
State the type of charge on the rod.
 
Explain your answer. 
[2]

3b
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1 mark

Electrical charges can move easily through some materials.

Draw a circle around each material that charges can move through easily.

copper plastic rubber silver wood

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4a
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4 marks

A student rubs a plastic rod with a dry cloth, as shown in Fig. 8.1. The rod becomes negatively charged.

rod
(i)
Use words from the box to complete the sentence.
air cloth electrons hand neutrons protons

  

The rod becomes negatively charged because ......................................... move from the ......................................... to the rod.

[2]

 

(ii)
The student moves the rod close to a suspended, charged rod. The two rods repel each other.
  
State the type of charge on the suspended rod.
[1]
 
(iii)
Explain your answer to (a)(ii).
[1]
4b
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2 marks

A device has a metal case. Any charge on the case must be able to move to earth.

     
(i)
Draw one ring around a material that is suitable for the connection to earth.
     
copper glass plastic rubber
[1]
 
(ii)
Explain your answer to (b)(i).
[1]

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5a
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1 mark

Fig. 10.1 shows the apparatus for an experiment on electrostatics.

cie-2019-15

Identify the pieces of equipment that are electrical conductors and those that are electrical insulators. Draw a line from each piece of equipment to the correct box.

 
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5b
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2 marks

State and explain how the polythene strip can be given a negative charge.

5c
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2 marks

Describe how the apparatus in Fig.10.1 could be used to demonstrate that the polythene strip has a negative charge.

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1a
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3 marks

A student rubs a polythene rod with a dry cloth. The polythene rod becomes negatively charged.

Describe and explain how the rod becomes negatively charged.

1b
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2 marks

The negatively charged polythene rod hangs from a nylon thread so that it is free to turn.

 The student charges a second polythene rod and brings it close to the first rod, as shown in Fig.11.1.

feb-march-2018-32-q11
 

Describe and explain what happens when the negatively charged rods are close to each other.

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2a
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2 marks

A student experiments with electric charge.

The student uses a dry cloth to rub a plastic rod. The rod becomes positively charged.

Explain how the friction between the rod and the cloth causes the rod to become positively charged.

Use your ideas about the movement of charge.

2b
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3 marks

The student suspends a balloon from an insulating thread, as shown in Fig. 9.1.

 

18p3-9b

The balloon has an electric charge.

 
Explain how the student can use a positively charged rod to determine the charge on the balloon.

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3a
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2 marks

The lamp of a car headlight is rated at 12 V, 50 W.

 
Calculate the current in the lamp when operating normally.

 

current = ......................................................... 

3b
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5 marks

A car is driven at night.

In a journey, the total charge that passes through the 12 V battery is 270 kC.

 

(i)

Calculate the electrical energy transferred.

energy = ......................................................... [3]

(ii)

The fuel used by the car provides 3.6 × 104 J / cm3.

 
Calculate the volume of fuel used to provide the energy calculated in (b)(i).

 

volume = ......................................................... [2]

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4a
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1 mark

Fig. 9.1 shows the symbol for a 12V battery.

18p4-9a

Two lamps are connected in parallel with the battery.

 

On Fig. 9.1, using the correct symbols, complete the circuit diagram.

4b
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3 marks

One of these lamps has a resistance of 6.0 Ω.

 
Calculate, for this lamp:

 
(i)
the current
 
 
current = ...........................................................[1]
 
(ii)
the power.
 
 
power = ...........................................................[2]
4c
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3 marks

The power of the other lamp is 36 W.

 
Calculate the total energy delivered to this lamp in 20 hours.

 
 
energy = ...........................................................

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5a
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2 marks

Fig. 9.1 shows current-potential difference graphs for a resistor and for a lamp.

feb-march-2018-42-q8

(i)
The potential difference (p.d.) applied to the resistor is increased. Tick the box that indicates the effect on the resistance of the resistor.
 

square resistance increases

square resistance is constant

square resistance decreases

 [1]
 
(ii)

The potential difference (p.d.) applied to the lamp is increased. Tick the box that indicates the effect on the resistance of the lamp.

   

square resistance increases

square resistance is constant

square resistance decreases

[1]

5b
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2 marks

The p.d. across the lamp is 6.0V. Calculate the resistance of the lamp.

 

resistance = ......................................................... 

5c
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2 marks

The lamp and the resistor are connected in parallel to a 6.0 V supply.

Calculate the current from the supply.

 

current = .........................................................

5d
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2 marks

The lamp and the resistor are connected in series to another power supply. The current in the circuit is 4.0 A.

Calculate the total p.d. across the lamp and the resistor.

 

 

p.d. = .........................................................

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6a
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1 mark

Fig. 10.1 shows a circuit used by a student to test a metal wire made of nichrome.

18-23-8a

State the name of component Z.

6b
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1 mark

The current reading on ammeter X is 0.8 A. State the reading on ammeter Y.

6c
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3 marks

The current in the nichrome wire is 0.8 A. The potential difference (p.d.) across the nichrome wire is 4.5 V.

Calculate the resistance of the nichrome wire.

 
 
resistance = ..................................................... Ω 
6d
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2 marks

The student tests a different nichrome wire, which is thicker than the wire in (c), but of the same length. When testing this wire, the current in the wire is different from the value given in (c).

 
State and explain the difference in current.

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7a
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5 marks

Fig. 10.1 shows an electrical circuit.

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(i)
State the name for the component labelled X and state its function in this circuit.
[2]
 
(ii)

Describe how the circuit shown in Fig. 10.1 could be used to find the resistance of the fixed resistor R.

[3]
7b
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4 marks

An electrical heater has a resistance of 21.8 Ω when connected to a 240 V mains supply.

 
(i)

Calculate the current in the heater.

 

 

current = ....................................................... A [3]

(ii)

Suggest a rating for the fuse to be fitted to the mains plug for the heater.

 

fuse rating = ....................................................... A [1]

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8a
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4 marks

An uncharged conducting metal plate rests on insulating supports. Fig. 10.1 shows the plate and a positively charged insulating plastic sheet placed on top of the metal plate.

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(i)

Describe any flow of charge that takes place when the plastic sheet is placed onto the metal plate.

[1]

(ii)

On Fig. 10.1, draw how charges are now arranged within the metal plate.

[1]

(iii)

State and explain if this arrangement of charge helps to keep the plastic sheet in place.

[2]

8b
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2 marks

Fig. 10.2 shows two uncharged conducting spheres suspended on insulating threads.

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(i)
The spheres are now both given positive charges. On Fig. 10.2, draw a possible position of each sphere and thread.

(ii)
Explain the positions you have drawn.

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1a
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1 mark

State, in terms of their structure, why metals are good conductors of electricity.

1b
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4 marks

A cylindrical metal wire W1, of length L and cross-sectional area A, has a resistance of 16 Ω.A second cylindrical wire W2 having length L over 2 and cross-sectional area 2A, is made from the same metal.

Determine

(i)

the resistance of W2,

 

 

resistance of W2 = ...........................................................[2]

(ii)

the effective resistance of W1 and W2 when connected in parallel

 

 

resistance of parallel pair = ...........................................................[2]

1c
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2 marks

The parallel pair of resistors in (b)(ii) is connected to a battery that is made from three cells in series, each of electromotive force (e.m.f.) E. There is a current in each resistor.

 
(i)
State the e.m.f. of the battery.
[1]
 
(ii)
The current in the battery is IB, the current in W1 is I1 and the current in W2 is I2.
 
Place a tick in one box to indicate how these three currents are related.
 
square  I1 > I2 > IB
square  I1 > IB > I2
square  I2 > I1 > IB
square  I2 > IB > I1
square  IB > I1 > I2
square  IB > I2 > I1
square  I1 = I2 = IB
[1]

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2a
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4 marks
(i)
Fig. 8.1 shows a positively charged cube of insulating material. The cube is fixed to a piece of wood that is floating on water. A negatively charged rod is held above the piece of wood and brought close to the cube, as shown.
 
q8i
State and explain any movement of the piece of wood.
[2]
 
(ii)
Fig. 8.2 shows two cubes of insulating material. One is positively charged and the other is negatively charged. The cubes are fixed to a piece of wood that is floating on water. Charged rods are held above the piece of wood and brought close to the cubes, as shown.
 
q8ii
State and explain any movement of the piece of wood. 
[2]
2b
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2 marks

In terms of a simple electron model, describe the differences between conductors and insulators.

2c
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1 mark

On Fig. 8.3, draw the electric field pattern around a single-point positive charge.

q8c

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3a
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2 marks
(i)
Describe what is meant by an electric field.
[1]
(ii)
State what is meant by the direction of an electric field.

 

[1]
3b
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4 marks

Fig. 8.1 shows a polystyrene ball covered with aluminium paint. The polystyrene ball is suspended between two charged metal plates by an insulated thread.

 q8

The ball oscillates between the two charged plates.
Explain why the ball oscillates.

3c
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3 marks

There is a current of 0.29 A in an electrical circuit.

Calculate the time taken for a charge of 15 C to flow through the electrical circuit.

 

 

time = .........................................................

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4a
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4 marks

A light-emitting diode (LED) is a diode that emits light when there is a current in it.

Draw a circuit diagram showing an LED, connected so that it is lit, in series with a battery and a fixed resistor. Use standard electrical symbols.

4b
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2 marks

The p.d. across the LED when lit is 3.1 V and the current in the LED is 0.030 A.


Calculate the value of the resistance of the LED when lit.

 

 

resistance = .........................................................

4c
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4 marks
Fig. 8.1 shows a power supply of e.m.f. 10.5 V connected in series with a lamp and a heater.

  
The p.d. across the lamp is 2.1 V and the current in the lamp is 1.5 A.

 
may-june-2020-42-q8
 

Calculate:

 
(i)

the resistance of the heater

 
 

resistance = ......................................................... [2]

(ii)

the power of the heater.

 
 

power = ......................................................... [2]

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5a
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2 marks

A light polystyrene ball is coated in conducting paint and suspended from a thread as shown in Fig. 1

The ball is given a positive charge

4-2-5a-h-charges-interacting-1-q

Fig. 1

Draw the field lines around the positively charged ball.

5b
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4 marks

A second, identical ball is suspended close to the first one. The second ball is also given a positive charge.

Marion says that both balls will hang straight downward, due to the effect of gravity.

State whether Marion is correct, and explain your answer.

5c
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4 marks

Sketch the arrangement of the two balls hanging next to each other.

Add field lines to your diagram, in support of your answer to part (b).

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