AQA AS Physics

Topic Questions

ASPhysicsAQATopic Questions5. Electricity5.1 Current–Voltage Characteristics

5.1 Current–Voltage Characteristics

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11 mark

What is the definition of electric current?

  • the rate of movement of electrons within a material that conducts electricity

  • the rate of flow of negative charge carriers

  • the rate of flow of positive charge carriers

  • the movement of atoms in a material

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21 mark

What is the correct equation linking current, charge and time?

  • Q = It

  • Q = EV

  • Q = begin mathsize 16px style I over t end style

  • Q = IV

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31 mark

What happens when two oppositely charged conductors are connected together by a length of wire?

  • Charge will jump between the two conductors

  • Charge builds up on the surface of one of the conductors

  • Charge cannot flow between the two conductors

  • Charge will flow between the two conductors, causing a current

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41 mark

Which statement is true about the flow of electrons and conventional current in an electric circuit?

 

Flow of Electrons

Conventional Current
A

In electrical wires the current is a flow of electrons

Conventional current is defined as the flow of negative charge
B

Electrons flow away from the negative to the positive terminal of a cell

Conventional current flows in the same direction as electron flow
C

Electrons are positively charged

Conventional current is defined as the flow of positive charge
D Electrons flow away from the negative to the positive terminal of a cell Conventional current flows in the opposite direction to electron current flow

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51 mark

What is the equation linking potential difference, work done and charge?

  • V = QW

  • Q = EV

  • V = begin mathsize 16px style W over Q end style

  • P = begin mathsize 16px style E over t end style

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61 mark

What are the correct units for current, resistance and potential difference?

 

Current (I)

Resistance (R)

Potential Difference (V)
A

Amperes

Ohms

Volts
B

Coulombs

Joules

Amperes
C

Meters per second

Coulombs

Joules
D

Joules

Resistivity

Coulombs

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71 mark

What is the correct equation for Ohm’s Law?

  • V = IR

  • Q = It

  • V =begin mathsize 16px style W over Q end style

  • P = begin mathsize 16px style E over t end style

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81 mark

What is the definition of Ohm’s Law?

  • The current through a conductor in a circuit is proportional to the potential difference across it

  • For a conductor at a constant temperature, the current through it is proportional to the potential difference across it

  • The resistance of a conductor is constant whilst the temperature remains constant

  • An increase in temperature of an Ohmic conductor will create an increase in current across the component

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91 mark

Which graph represents the current-voltage characteristic of an ohmic conductor?

q9_currentvoltage-characteristics_aqa-as-physics-mcq

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101 mark

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

Which statements correctly describe the current-potential difference graph for a semiconductor diode?

 

Statement 1

Statement 2
A

When the current flows in the direction of the diode, there is a sharp increase in potential difference and current on the right side of the graph

When the diode is reversed, it conducts electricity and this is shown by a sharp increase in potential difference and current on the right side of the graph
B

When the current flows in the direction of the diode, then it does not conduct and this is shown by a zero on the right hand side of the graph

When the diode is reversed, it does not conduct electricity and this is shown by a zero on the left hand side of the graph
C

When the current flows in the direction of the diode, there is a sharp increase in potential difference and current on the right side of the graph

When the diode is reversed, it does not conduct electricity and this is shown by a zero on the left hand side of the graph
D

When the current flows in the direction of the diode, then it does not conduct and this is shown by a zero on the right hand side of the graph

When the diode is reversed, it does not conduct electricity and this is shown by a zero on the left hand side of the graph

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11 mark

The graph shows how the potential difference V across an electrical component varies with current I in the component.

A tangent has been drawn on the curve at point P for a current of I2.

q21_currentvoltage-characteristics_aqa-as-physics-mcq

What is the resistance of the electrical component when the current in the component is I2?

  • begin mathsize 16px style fraction numerator V subscript 3 minus V subscript 1 over denominator I subscript 3 minus I subscript 1 end fraction end style

  • begin mathsize 16px style fraction numerator V subscript 3 minus V subscript 1 over denominator 2 I subscript 2 end fraction end style

  • begin mathsize 16px style fraction numerator 2 V subscript 2 over denominator I subscript 2 minus I subscript 1 end fraction end style

  • begin mathsize 16px style V subscript 2 over I subscript 2 end style

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21 mark

The simple series circuit is set up and the terminal voltage of the supply is set to 6 V. The bulb has an efficiency of 80% and over a period of 10 s, 450 J of light energy is recorded as emitted by the bulb.

q22_currentvoltage-characteristics_aqa-as-physics-mcq

What is the resistance of the bulb?

  • 0.11 Ω

  • 0.64 Ω

  • 0.80 Ω

  • 1.00 Ω

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31 mark

The speed of electrons in a conductor can be calculated using the equation

                                                      I = nAve

where I is the current in A, n is the number of electrons per m3, A is the cross sectional area in m2, v is the average velocity of electrons in m s–1 and e is the charge on one electron which is 1.6 × 10–19 C.

The circuit below is set up to measure the speed of electrons in copper.

q23_currentvoltage-characteristics_aqa-as-physics-mcq

For copper, n = 8.5 × 1028 per m3.

The voltage of the supply is 12 V and the diameter of the wire is 2.4 mm. In 10 seconds, the wire transforms 240 J of electrical energy into heat energy.

 What is the average velocity of the electrons in the wire?

  • 8.13 × 10–6 m s–1

  • 3.25 × 10–11 m s–1

  • 8.13 × 10–12 m s–1

  • 3.25 × 10–5 m s–1

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41 mark

A 2 Ω resistor and a 4 Ω resistor are connected to a cell.

q24_currentvoltage-characteristics_aqa-as-physics-mcq

Which graph shows how the potential V varies with distance between X and Y?

q24-2_currentvoltage-characteristics_aqa-as-physics-mcq

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51 mark

A resistor and a diode are connected in parallel and connected to a d.c. supply.

q25_currentvoltage-characteristics_aqa-as-physics-mcq

What is the correct graph of current against voltage for the circuit?

q25-2_currentvoltage-characteristics_aqa-as-physics-mcq

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61 mark

In biology, there is a field called electrophysiology. This is where charged ions of sodium (Na+) and potassium (K+) pass through cell membranes creating a potential difference between the two sides of the cell. Nerve cells work on this principle and allow transmission of messages using action potentials.

We can plot an approximate graph of the sodium and potassium components of the cell’s current and voltage characteristic. The lines on this graph show the potassium component and the overall I-V curve.

q26_currentvoltage-characteristics_aqa-as-physics-mcq

Which of the following sketch graphs could represent the I-V characteristic for the Na+ ion?

q26-2_currentvoltage-characteristics_aqa-as-physics-mcq

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71 mark

The following circuit is built including a charge carrying copper wire of length 1 m and mass 72 grams.

q27_currentvoltage-characteristics_aqa-as-physics-mcq

The wire hovers in a horizontal magnetic field of magnitude 0.23 T when  a current passes through it. A horizontal magnetic field will produce a vertical force on a charge carrying wire.

 The force on the wire can be found using the equation

                                                                     F = B I space l

 Where F is force in N, B is magnetic field strength in T, I is the current in A and l is the length of the wire in metres.

 A current flows in this wire for 0.4 mins.

 What is the charge transferred in this time?

  • 3.1 C

  • 7.5 C

  • 1200 C

  • 74 C

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81 mark

Resistivity,space rho, is a property that describes the extent to which a material opposes the flow of electric current through it. It can be calculated using the equation

                                                                    rho = begin mathsize 16px style fraction numerator R A over denominator L end fraction end style

Where R is the resistance in Ohms, A is the cross sectional area of the wire in m2 and L is the length of the material in m.

Which of the following cannot be the units for resistivity?

  • fraction numerator size 16px J size 16px space size 16px m over denominator size 16px C size 16px A end fraction

  • fraction numerator size 16px V size 16px space size 16px s size 16px space size 16px m over denominator size 16px C end fraction

  • fraction numerator size 16px J over denominator size 16px s size 16px space size 16px A size 16px space size 16px m end fraction

  • fraction numerator size 16px V size 16px space size 16px m over denominator size 16px A end fraction

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91 mark

A circuit contains an LED and a thermistor connected in series and powered by a 9V DC supply.

The I-V characteristic of the LED is shown in this graph

q29-1_currentvoltage-characteristics_aqa-as-physics-mcq

The resistance vs temperature relationship for the thermistor are shown in the second graph below

q29-2_currentvoltage-characteristics_aqa-as-physics-mcq

The light from the LED becomes visible when the current through it is 0.28 A. 

What is the temperature when the LED turns on?

  • 40 o C

  • 28 o C

  • 35 o C

  • 24 o C

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101 mark

The figure below shows the current-voltage characteristic for a photovoltaic solar cell.

q30_currentvoltage-characteristics_aqa-as-physics-mcq

 Two of these cells are connected in parallel to power a circuit.

 If circuit is operating at 5.5 V, what percentage of the maximum possible power is being used?

  • 96 %

  • 62 %

  • 50 %

  • 43 %

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11 mark

A charge of 8.0 C passes through a resistor of resistance 30 Ω at a constant rate in a time of 20 s.

What is the potential difference across the resistor?

  • 0.40 V

  • 5.3 V

  • 12 V

  • 75 V

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21 mark

The graph shows how current I varies with voltage V for a filament lamp.

q12_currentvoltage-characteristics_aqa-as-physics-mcq

Since the graph is not a straight line, the resistance of the lamp varies with V.

Which row gives the correct resistance at the stated value of V?

 

V / V

R / Ω
A

2.0

1.5
B

4.0

3.2
C

6.0

1.9
D 8.0 0.9

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31 mark

The potential difference across a component in a circuit is 2.0 V.

How many electrons must flow through this component in order for it to be supplied with 4.8 J of energy?

  • 2.6 × 1018

  • 1.5 × 1019

  • 3.0 × 1019

  • 6.0 × 1019

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41 mark

A milliammeter shows a reading of 20 mA.

How many electrons flow through the milliammeter in 10 seconds?

  • 0.20

  • 3.2 × 1020

  • 200

  • 1.3 × 1018

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51 mark

The resistance R of a resistor is to be determined. The current I in the resistor and the potential difference V across it are measured.

The results, with their uncertainties, are

                                    I = (2.0 ± 0.2) A                     V = (15.0 ± 0.5) V

What is the uncertainty in this value for R?

  • ± 0.3 Ω

  • ± 0.5 Ω

  • ± 0.7 Ω

  • ± 1 Ω

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61 mark

The current in the circuit shown is 4.8 A

q16_currentvoltage-characteristics_aqa-as-physics-mcq

What is the direction of flow and the rate of flow of electrons through the resistor R?

 

direction of flow

rate of flow
A

X to Y

3.0 × 1019 s–1
B

X to Y

6.0 × 1018 s–1
C

Y to X

3.0 × 1019 s–1
D Y to X 6.0 × 1018 s–1

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71 mark

The variation with potential difference V of the current I in a semiconductor diode is shown below.

q17_currentvoltage-characteristics_aqa-as-physics-mcq

What is the resistance of the diode for applied potential differences of +1.0 V and –1.0 V?

 

resistance
at +1.0 V

resistance
at –1.0 V
A

20 Ω

infinite
B

20 Ω

zero
C

0.05 Ω

infinite
D 0.05 Ω zero

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81 mark

A battery of negligible internal resistance is connected to two 10 Ω resistors in series.

q18_currentvoltage-characteristics_aqa-as-physics-mcq

What charge flows through each of the 10 Ω resistors in 1 minute?

  • 0.30 C

  • 0.60 C

  • 3.0 C

  • 18 C

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91 mark

The graph shows the voltage-current graph of a filament wire.

q19_currentvoltage-characteristics_aqa-as-physics-mcq

What is the resistance of the wire when it obeys Ohm’s law?

  • 10 Ω

  • 10 kΩ

  • 0.1 mΩ

  • 0.1 Ω

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101 mark

The diagram shows a length of track from a model railway connected to a battery, a resistor and a relay coil.

q20_currentvoltage-characteristics_aqa-as-physics-mcq

With no train present, there is a current in the relay coil which operates a switch to turn on a light.

When a train occupies the section of track, most of the current flows through the wheels and axles of the train in preference to the relay coil. The switch in the relay turns off the light.

Why is a resistor placed between the battery and the track?

  • to limit the heating of the wheels of the train

  • to limit the energy lost in the relay coil when a train is present

  • to prevent a short circuit of the battery when a train is present

  • to protect the relay when a train is present

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