Electricity questions

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Electricity question collection

Review Electricity questions for Physics, with correct answers shown and coverage across current, potential difference and resistance; series and parallel circuits; circuit components.

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Question 1

What causes an electric current through a conductor?
  1. A flow of electrical charge carriers (electrons)
  2. Static charges that stay still
  3. A transfer of heat alone
  4. Magnetic poles moving past each other

Question 2

Which unit is used to measure electric current?
  1. Ampere (A)
  2. Volt (V)
  3. Ohm (Ω)
  4. Joule (J)

Question 3

What is potential difference (voltage)?
  1. The energy transferred per unit charge between two points
  2. The current lost per second
  3. The resistance of the wire
  4. The temperature of the source

Question 4

What does resistance describe?
  1. How much a component opposes the current
  2. How fast charges move past each other
  3. The number of electrons in the wire
  4. The brightness of a bulb

Question 5

In a series circuit, what is true about the current?
  1. It is the same through every component
  2. It splits so every branch has a different current
  3. It is zero everywhere
  4. It only flows through the battery

Question 6

In a parallel circuit, how does the potential difference behave?
  1. It is the same across each branch
  2. It is zero in every branch
  3. It is different for each branch
  4. It does not exist until a switch is closed

Question 7

What happens to the total resistance when resistors are added in series?
  1. The total resistance increases
  2. The total resistance decreases
  3. It stays constant
  4. It becomes zero

Question 8

Which material is a good electrical conductor?
  1. Copper
  2. Plastic
  3. Glass
  4. Dry wood

Question 9

What does a fuse do in a plug?
  1. Melts when current is too high to stop the flow
  2. Increases the voltage instantly
  3. Merges live and neutral wires
  4. Charges the earth wire permanently

Question 10

Why is the earth wire included in appliances?
  1. To provide a safe route for fault currents
  2. To carry the main voltage
  3. To light the bulb
  4. To store charge for later

Question 11

In the UK, what color is the live wire that carries ~\(230\,\mathrm{V}\)?
  1. Brown
  2. Blue
  3. Green
  4. White

Question 12

What happens when you open a switch in a circuit?
  1. The circuit breaks and current stops flowing
  2. The current gets ten times bigger
  3. The wires get colder instantly
  4. The potential difference doubles

Question 13

When current flows through a resistor what does the electrical energy become?
  1. Thermal energy (and sometimes light)
  2. Chemical energy only
  3. Magnetic energy that never leaves
  4. Potential difference stored up

Question 14

Where should an ammeter go to measure the current through a component?
  1. In series with the component
  2. Across the component (in parallel)
  3. Next to the plug socket without touching the circuit
  4. Only in the earth wire

Question 15

Where should a voltmeter be placed when measuring potential difference?
  1. In parallel across the component being measured
  2. In series with the component
  3. Anywhere in the circuit as long as it is switched off
  4. Between live and earth only

Question 16

How is static electricity produced?
  1. By rubbing insulating materials so electrons transfer
  2. By linking wires in parallel
  3. By heating a wire until it glows
  4. By holding a magnet near a metal

Question 17

What happens to two objects with the same type of electric charge?
  1. They repel each other
  2. They always attract instantly
  3. They explode with light
  4. They stop conducting electricity

Question 18

Which equation links potential difference \(V\), current \(I\) and resistance \(R\)?
  1. \(V = IR\)
  2. \(V = \frac{I}{R}\)
  3. \(V = I + R\)
  4. \(V = \frac{R}{I}\)

Question 19

If the potential difference across a resistor increases, what happens to the current?
  1. The current increases
  2. The current becomes zero
  3. The current flows backwards
  4. The current does not change at all

Question 20

Why are electrical wires covered in insulating material?
  1. To prevent electric shocks and keep the current inside
  2. To make the wires heavier
  3. To conduct more current
  4. To decrease the potential difference

Question 21

A torch uses a \(9\,\mathrm{V}\) battery and a \(3\,\mathrm{\Omega}\) bulb. What current flows?
  1. \(3\,\mathrm{A}\)
  2. \(0.33\,\mathrm{A}\)
  3. \(6\,\mathrm{A}\)
  4. \(9\,\mathrm{A}\)

Question 22

Charge flow is given by \(Q = It\). How much charge passes through a wire when \(3\,\mathrm{A}\) flows for \(10\,\mathrm{s}\)?
  1. \(30\,\mathrm{C}\)
  2. \(300\,\mathrm{C}\)
  3. \(13\,\mathrm{C}\)
  4. \(0.3\,\mathrm{C}\)

Question 23

Ohm's law states \(V = IR\). What potential difference does a \(5\,\mathrm{\Omega}\) resistor have if the current is \(2\,\mathrm{A}\)?
  1. \(10\,\mathrm{V}\)
  2. \(7\,\mathrm{V}\)
  3. \(2.5\,\mathrm{V}\)
  4. \(50\,\mathrm{V}\)

Question 24

Which graph best represents an ohmic conductor?
  1. A straight line through the origin
  2. A curve that flattens as \(V\) increases
  3. A parabola opening downward
  4. A horizontal line

Question 25

Why is the I–V graph for a filament lamp curved?
  1. The resistance increases as the filament heats up
  2. The resistance decreases to zero
  3. The resistance stays constant
  4. The resistance becomes negative

Question 26

Which equation links power \(P\), potential difference \(V\), and current \(I\)?
  1. \(P = VI\)
  2. \(P = \frac{V}{I}\)
  3. \(P = V + I\)
  4. \(P = \frac{I}{V}\)

Question 27

Which form of electricity supply is used in UK homes?
  1. Alternating current at \(230\,\mathrm{V}\), \(50\,\mathrm{Hz}\)
  2. Alternating current at \(120\,\mathrm{V}\), \(60\,\mathrm{Hz}\)
  3. Direct current at \(230\,\mathrm{V}\)
  4. Direct current at \(50\,\mathrm{V}\)

Question 28

Why do power stations use step-up transformers before the National Grid?
  1. To raise voltage so the current is lower and energy losses drop
  2. To lower voltage so it can run machines
  3. To convert to direct current
  4. To increase the current to dangerous levels

Question 29

An appliance rating is \(2\,\mathrm{kW}\). How much energy does it use in \(5\,\mathrm{min}\) (\(300\,\mathrm{s}\))?
  1. \(600\,\mathrm{kJ}\)
  2. \(6\,\mathrm{J}\)
  3. \(60\,\mathrm{kJ}\)
  4. \(6000\,\mathrm{J}\)

Question 30

Charge of \(4\,\mathrm{C}\) flows through a component with \(5\,\mathrm{V}\) across it. How much energy is transferred?
  1. \(20\,\mathrm{J}\)
  2. \(0.8\,\mathrm{J}\)
  3. \(9\,\mathrm{J}\)
  4. \(20\,\mathrm{kJ}\)

Question 31

Why do series circuits have the same current through each component?
  1. The current has only one path to follow
  2. The current splits evenly across branches
  3. The current stops entirely after one component
  4. The current circulates only in the earth wire

Question 32

In parallel circuits, what is the potential difference across each branch?
  1. The same
  2. Different for each branch
  3. Zero
  4. Twice the supply voltage

Question 33

What is the purpose of the fuse in a plug?
  1. It melts when too much current flows, breaking the circuit
  2. It measures voltage
  3. It keeps the circuit closed in a fault
  4. It stores energy

Question 34

Why do double-insulated appliances not need an earth wire?
  1. Their design prevents live parts becoming exposed
  2. They carry no current
  3. They are connected to neutral only
  4. They rely on a second fuse

Question 35

Which equation shows the link between power, current and resistance?
  1. \(P = I^2R\)
  2. \(P = I + R\)
  3. \(P = \frac{I}{R}\)
  4. \(P = IR^2\)

Question 36

Which equation gives the energy transferred by electrical work using power and time?
  1. \(E = Pt\)
  2. \(E = \frac{P}{t}\)
  3. \(E = P + t\)
  4. \(E = P^2 t\)

Question 37

Which property of the live wire makes it dangerous even when the switch is open?
  1. It can still be at \(230\,\mathrm{V}\) relative to earth
  2. It carries double the current
  3. It is always insulated
  4. It is always connected to earth

Question 38

Why are thermistors used in thermostats?
  1. Their resistance decreases as temperature increases
  2. Their resistance increases as temperature increases
  3. Their resistance stays constant
  4. Their resistance becomes infinite at high temperature

Question 39

When do light-dependent resistors (LDRs) have lower resistance?
  1. When light intensity increases
  2. When light intensity decreases
  3. When they are cooled
  4. When they are stretched

Question 40

Why do step-down transformers in domestic supplies reduce voltage?
  1. Appliances need a lower, safer voltage
  2. It increases power unexpectedly
  3. It turns AC to DC
  4. It lowers the current to zero

Question 41

Which ratio describes an ideal transformer?
  1. \(\frac{V_p}{V_s} = \frac{N_p}{N_s}\)
  2. \(\frac{V_p}{V_s} = \frac{N_s}{N_p}\)
  3. \(V_p V_s = N_p N_s\)
  4. \(V_p = V_s\)

Question 42

Why is copper used for wires?
  1. Low resistance allowing easy current flow
  2. High resistance
  3. Magnetic properties
  4. It glows red when cold

Question 43

In a parallel circuit, what happens when one branch is closed?
  1. Does not stop other branches carrying current
  2. Stops all current
  3. Raises voltage only in closed branch
  4. Shorts the entire circuit

Question 44

How does a resistor heating element change as it warms up?
  1. Its resistance increases, so current drops for given voltage
  2. Resistance drops
  3. Current rises to infinity
  4. It produces magnetic flux only

Question 45

Describe the role of earth wire in a plug?
  1. Provides safe route for fault current to earth
  2. Carries the main voltage
  3. Makes appliance positive
  4. Stores electricity

Question 46

Which statement about series bulbs is true?
  1. They share the total potential difference
  2. Each has same current but different voltage
  3. Only one burns at a time
  4. Bulbs cool down the circuit

Question 47

A \(12\,\mathrm{V}\) battery supplies two resistors of \(4\,\mathrm{\Omega}\) and \(6\,\mathrm{\Omega}\) in series. What current flows?
  1. \(1.2\,\mathrm{A}\)
  2. \(2\,\mathrm{A}\)
  3. \(0.5\,\mathrm{A}\)
  4. \(10\,\mathrm{A}\)

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Review Electricity questions for Physics, with correct answers shown and coverage across current, potential difference and resistance; series and parallel circuits; circuit components.

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