AQA AS Physics

Topic Questions

5.1 Current–Voltage Characteristics

1a3 marks

Electric current is defined as the rate of flow of charge. 

Calculate the total charge transferred through a lamp if a current of 0.3 mA flows for 5 minutes.

1b3 marks

Figure 1 shows a typical electric circuit involving a battery, lamp and two resistors. 

There is a gap in the circuit between points X and Y.  

Figure 1

5-1-s-q--q1b-easy-aqa-a-level-physics

Draw on Figure 1: 

(i)
An ammeter between X and Y that would measure the current in the circuit 
(ii)
The direction of conventional current in the circuit

          

1c2 marks

With reference to the terminals of the battery, define the term ‘electron flow’ in an electric circuit. 

1d2 marks

Calculate the number of electrons flowing through the lamp in part (a) if the total charge transferred through it is 2.0 C. 

Did this page help you?

2a4 marks

Define the following in words: 

   (i)   The potential difference across a component 

   (ii)   The resistance of a component

2b5 marks

Figure 1 shows an electric circuit consisting of a battery, of emf 6 V, a variable resistor, two fixed resistors, an ammeter and a voltmeter. 

Figure 1

5-1-s-q--q2b-easy-aqa-a-level-physics

The following information is given: 

  • Voltmeter reading = 4 V
  • Ammeter reading = 2 A
  • Fixed resistors have a resistance R = 2 Ω 

Calculate: 

(i)
The charge transferred through the variable resistor in 2 hours 
(ii)
The energy transferred across the variable resistor in 2 hours

  

2c3 marks

Calculate the current through the fixed resistor R1 in Figure 1.

2d2 marks

A fixed resistor is often described as an ‘Ohmic conductor’. 

Ohm’s Law describes the conditions which are satisfied by all ohmic conductors. 

State Ohm’s Law in words.

Did this page help you?

3a3 marks

The potential difference and current through various electric components are often characteristic. 

On the axes provided in Figure 1, sketch the characteristic graph of current I against potential difference V for a filament lamp. 

Figure 1

5-1-s-q--q3a-easy-aqa-a-level-physics

3b3 marks

A student carries out an experiment to determine the resistance of two unmarked resistors, A and B. 

The student collects a battery pack, an ammeter, a voltmeter, and a variable resistor.   

Sketch a circuit that would determine the resistance of resistor A or B using the equipment the student collects.

3c2 marks

The student plots the results of the experiment on a graph of current I against potential difference V as shown in Figure 2: 

Figure 2

5-1-s-q--q3c-easy-aqa-a-level-physics

State and explain which resistor, A or B, has the larger resistance.

3d3 marks

Use Figure 2 to calculate the resistance of the resistor B.

Did this page help you?

4a3 marks

Three IV graphs, A, B, and C are shown in Figure 1: 

Figure 1

5-1-s-q--q4a-easy-aqa-a-level-physics

State which graph, A, B, or C is the characteristic IV graph for: 

   (i)    A filament lamp 

   (ii)   A fixed resistor 

   (iii)  A semiconductor diode

4b3 marks

Sometimes, the quantities on the axes are switched, such that potential difference V is on the vertical axis, and current I is on the horizontal axis like that shown in Figure 2. These are called V graphs. 

Figure 2

5-1-s-q--q4b-easy-aqa-a-level-physics

Sketch a V–I graph corresponding to a filament lamp on the axes provided in Figure 2.

4c1 mark

State the quantity that is represented by the gradient of a V–I graph.

4d2 marks

A semiconductor diode only allows current to flow in a specific direction. 

Figure 3 shows a circuit used to investigate the potential difference and current for a semiconductor diode; however, the semiconductor diode is yet to be connected. 

Figure 3

5-1-s-q--q4d-easy-aqa-a-level-physics

Complete the circuit diagram in Figure 3 to show how a semiconductor diode is connected in a forward bias

Did this page help you?

5a2 marks

The Standard International System of Units(SI) is a system of measurement based on seven base units. 

State the symbol and the SI unit for electric charge.

5b3 marks

Electric current is defined as the rate of flow of electric charge.

(i)
State the particle responsible for carrying electric charge around a circuit 
(ii)
Calculate the total electric charge carried by ten million of these particles

5c2 marks

State the symbol and the SI unit for potential difference. 

5d3 marks

Electric charge and potential difference are related. 

(i)
State an equation that relates electric charge and potential difference 
(ii)
Hence, or otherwise, express one joule in terms of units of potential difference and electric charge

Did this page help you?

1a4 marks

Figure 1 shows two electrons orbiting a helium nucleus with an orbital radius of 448 pm.  The total kinetic energy of the electrons in orbit is 4.61 × 10–18 J. 

Figure 1

5-1-s-q--q1a-hard-aqa-a-level-physics

Calculate the size of the current created by the motion of the electrons orbiting the helium nucleus. 

1b4 marks

When helium gas is placed between two electrodes with a high potential difference across them the helium atoms lose electrons and H e to the power of 2 plus end exponent ions are formed. 

The gas carries a current of 8.16 mA and the number of electrons passing any point in the gas per unit time is 2.58 × 1016 s–1. 

Calculate the number of helium ions which will pass any point in the gas per unit time.

1c2 marks

A cyclotron is used to accelerate charged particles outwards from the centre of a flat cylindrical vacuum chamber along a spiral path. 

During an experiment the cyclotron produces a beam of alpha particles which are directed towards a target.  The beam of alpha particles produces a current of 0.250 mA.  

Calculate how long it would take for 1 mole of alpha particles to strike the target.

Did this page help you?

2a4 marks

A student wishes to determine the resistance for three different resistors. They connect the resistors in a ‘T’ arrangement and change the position of the power source and the voltmeter, as shown in Figure 1, to obtain two sets of results, as shown in Table 1. The power supply in Circuit 1 causes a current of 0.50 A 

Figure 1

5-1-s-q--q2a-hard-aqa-a-level-physics

Table 1

Circuit

Voltage supplied by power source /V

Reading on voltmeter /V

1

8.0

5.0

2

10

4.0

 

Calculate the resistance of resistors R subscript 1R subscript 2 and R subscript 3.  

You may assume the voltmeter has an infinitely high resistance.

 

2b4 marks

A charge of 2 µC flows through a resistor when there is a potential difference of 4 V across it. 

Calculate the amount of electrical energy each electron will lose as it passes through the resistor and state what happens to this energy.

2c3 marks

When investigating whether or not a resistor is an ohmic conductor state and explain which variable must be kept constant and how is this achieved.

Did this page help you?

3a2 marks

An electron in a cathode ray tube is accelerated from rest through a potential difference of 150 kV and aimed towards a screen. 

Calculate the kinetic energy of the electrons when they collide with the screen.

3b3 marks

If the current in the tube is 32 mA, calculate the rate at which the heat must be dissipated from the screen when it reaches its working temperature.

3c3 marks

A travellator of width 50 cm has a surface containing a layer of electrons.  It moves through a brush, which collects the electrons and transports them away as electric current, at a speed of 5 m s–1Figure 1 shows the arrangement of the conveyor belt and the brush.

Figure 1

5-1-s-q--q3c-hard-aqa-a-level-physics

Given that there are 10 000 electrons per mm2 of the travellator, calculate the magnitude of the electric current through the wire brush.

Did this page help you?

4a5 marks

Figure 1 shows the variation in the current flowing through a filament lamp after it has been switched on. 

Figure 1

5-1-s-q--q4a-hard-aqa-a-level-physics

Use Figure 1 to explain the variation of current flowing through the filament lamp after it has been switched on.

4b2 marks

On Figure 1, draw the variation of current with time if the filament lamp had been stored at a colder temperature before being switched on.

4c4 marks

Given that the filament lamp is 15% efficient, calculate the amount of light energy produced when the lamp is switched on for 30 minutes after being connected to a 12.0 V d.c supply. 

You can assume that the time taken to reach the normal operating temperature is negligible compared to the time the lamp is switched on for.

Did this page help you?

5a2 marks

A beam of electrons, each of charge e, travels in a straight line with a uniform velocity, v.  

If the number of electrons per unit length of the beam is N, write an expression for the current produced by the beam in terms of N, e and v.

5b3 marks

Four small identical conductors, each of charge +3e, are fixed on the edge of a circular insulating disc, as shown in Figure 1.The disc rotates at 100 revolutions per second.  

Figure 1

5-1-s-q--q5b-hard-aqa-a-level-physics

Calculate the magnitude of the charge of the electrical current at the edge of the disc.

Did this page help you?

1a4 marks

A filament lamp rated 15 V, 1.0 A has a resistance of 3.0 Ω when it carries no current. 

Figure 1

5-1-s-q--q1a-medium-aqa-a-level-physics

On the axes in Figure 1, sketch the form of the current against voltage characteristic for this lamp.

1b5 marks

Explain why, as the voltage is increased either positively or negatively from zero, the characteristic has the form shown in your answer for part (a).

1c3 marks

Using your answer from part (b), explain, in terms of electron flow how the resistance of the filament lamp changes as the current in the lamp increases.           

1d2 marks

Figure 2 shows part the current-voltage (I-V) characteristic of a lamp up to its working voltage. 

Figure 2

5-1-s-q--q1d-medium-aqa-a-level-physics

Calculate the resistance in the lamp when 0.5 A of current is passed through it.

Did this page help you?

2a2 marks

Figure 1

5-1-s-q--q2a-medium-aqa-a-level-physics

On Figure 1, sketch the I-V characteristic of a silicon semiconductor diode for forward bias.

Indicate approximate values on the voltage axis.

2b3 marks

On Figure 1, sketch the I-V characteristic of a silicon semiconductor diode for reverse bias.

Indicate approximate values on the voltage axis.

2c4 marks

Describe, with references to the characteristic you have drawn, how the resistance of the diode varies with the potential difference across its terminals for reverse bias and for forward bias.

2d2 marks

A resistor and the semiconductor diode are connected in series with a variable power supply as shown in Figure 2.

Figure 2

5-1-s-q--q2d-medium-aqa-a-level-physics

Draw the I-V characteristic for the combination of the resistor and diode bias on Figure 3.

Figure 3

5-1-s-q--q2d-fig-1-medium-aqa-a-level-physics

Did this page help you?

3a3 marks

In a wire, 8.3 × 1015 electrons pass through a point in 45 s. 

Calculate the current that this represents.

3b3 marks

A different wire carries a current of 50 mA. 

Calculate the number of electrons passing a point in this wire in 2.5 minutes.

3c3 marks

In a test to find the suitable metal wire to use for a fuse, the following graph shown in Figure 1 of current, I, against time, t, was obtained. The circuit, which was connected to a constant source of emf, was switched on at t = 0 s. 

Figure 1

5-1-s-q--q3c-medium-aqa-a-level-physics

The maximum current through the wire before the fuse melted was 3.6 A. 

Calculate the total charge that flowed during this test.

3d2 marks

The metal wire is then connected to a circuit with a 15 V cell. The total charge through the wire is equal to that during the fuse test.

Calculate the energy transferred in moving the total charge through the metal wire.

Did this page help you?

4a2 marks

The current-voltage characteristic of a fixed resistor is shown in Figure 1. 

Figure 1

5-1-s-q--q4a-medium-aqa-a-level-physics

Calculate the resistance of the fixed resistor.

4b2 marks

The fixed resistor is an example of an ohmic electrical component. 

Explain how Figure 1 shows that the resistor is an ohmic electrical component.

4c2 marks

Sketch, on Figure 1, the current-voltage characteristic of a resistor with a larger resistance. Explain why you have drawn the graph in this way.

4d4 marks

Calculate the work done by the charge flowing through the resistor when a current of 1.6 A flows through it in 1.5 minutes. 

Did this page help you?

5a2 marks

In an attempt to investigate how the resistance of a filament lamp varies with current through a lamp, a student obtains the results shown in Table 1. 

Table 1

Voltage / V

0.50

1.50

3.00

4.50

6.00

12.00

Current / A

0.80

1.50

2.20

2.80

3.20

4.00

Resistance / Ω

 

 

 

 

 

 

 

Complete Table 1 by calculating the corresponding values of resistance to an appropriate number of significant figures.

5b3 marks

Figure 1

5-1-s-q--q5b-medium-aqa-a-level-physics

On Figure 1, plot a graph of resistance against current for the filament lamp.

5c4 marks

Using your graph from part (b), state and explain the relationship between the current and resistance in the filament lamp.

5d2 marks

Hence, or otherwise, state and explain whether a filament lamp is an ohmic or non-ohmic conductor.

Did this page help you?