Electrical current

A charge of $7.5\,\text{C}$ passes through a resistor in $5.0\,\text{s}$. A student has ammeters of several different ranges available to measure the current in the resistor. Which ammeter range would be the most suitable?

May/June 2015

A car headlamp carries a current of $2.0\,\text{A}$. The headlamp remains switched on for $4.0\,\text{minutes}$. How much charge flows through the headlamp?

May/June 2016

A total charge of $45\ \text{C}$ passes through an electric appliance over $3.0\ \text{minutes}$. What is the average current in the appliance?

May/June 2016

A student constructs an electromagnet by winding a length of wire round a piece of soft iron and linking it into a circuit, as illustrated in Fig. 1.1. He then closes the switch and determines the greatest number of paperclips that remain attached to one end of the soft iron.

May/June 2016

In a thunderstorm, a lightning flash happens when charge moves between a cloud and the Earth. On average, $20\,\text{C}$ of charge is transferred in each flash, and there are three flashes each minute. What is the average current between the cloud and the Earth during the thunderstorm?

May/June 2017

The circuit shown remains switched on for $1.0$ minute. What amount of charge passes through the $3.0\,\Omega$ resistor?

May/June 2017

The cable for an electric cooker includes a live wire, a neutral wire and an earth wire. While the cooker is operating correctly, in which wires are the currents equal?

May/June 2019

A circuit is shown in the diagram. The ammeter can be set to four different ranges. Which range setting would give a reading close to the midpoint of the range?

May/June 2021

In which case is the current $1.0\,\text{A}$?

May/June 2021

A metal conductor is joined across the positive and negative terminals of a battery. Which row shows the direction in which the particles that move through the conductor travel, and what are they called?

May/June 2023

A $12\,\text{V}$ battery is connected to a resistor with resistance $100\,\Omega$. How much charge flows through the resistor in $30\,\text{minutes}$?

May/June 2025

A circuit includes a resistor placed between the positive terminal and the negative terminal of a power supply. Which row shows the direction of conventional current and the direction in which free electrons move in the resistor?

May/June 2025

A camera flash works as a capacitor discharges through a flash-tube. During $3.2\,\text{ms}$, a charge of $6.0\,\text{C}$ flows through the flash-tube. What is the mean current in the flash-tube?

Oct/Nov 2015

Inside a car’s engine compartment, the battery delivers a current of 120 A to the starter motor.

Oct/Nov 2017

A defibrillator is a piece of equipment used to deliver an electric shock to a patient’s heart. It delivers an electric shock with energy $240\ \text{J}$ at an average voltage of $2000\ \text{V}$ over $10\ \text{ms}$. What is the average current it supplies?

Oct/Nov 2018

A student is examining how the current in a thermistor varies with temperature. She assembles the circuit shown in Fig. 1.1. She adds hot water to the beaker. She stirs the water, measures the temperature and checks the ammeter. She enters the temperature and current values in the table in Fig. 1.2. She then repeats the readings at $10\,^{\circ}\text{C}$ intervals while the water cools, until room temperature is reached. She puts all the results into the table, as shown in Fig. 1.2. Fig. 1.3 gives the ammeter reading when the water temperature is $40\,^{\circ}\text{C}$.

Oct/Nov 2018

A student proposes four conditions for producing a continuous stream of electrons from a metal filament. Which of these four conditions are necessary?

Oct/Nov 2019

A car battery supplies $150\,\text{kC}$ of charge to a circuit before recharging becomes necessary. Two headlamps connected in parallel to the battery are turned on. Each lamp carries a current of $4.0\,\text{A}$. What time elapses before the battery needs recharging?

Oct/Nov 2020

A $240\ \text{V}$ mains circuit has eight $60\ \text{W}$ lamps connected in parallel. At the instant the lamps are switched on, the filaments are cold, and the current is four times the final steady current in the circuit. What is the initial current supplied by the mains?

Oct/Nov 2020

EITHER Fig. 5.1 presents a circuit that includes a direct current (d.c.) power supply, a light-dependent resistor (LDR), two fixed resistors, M and N, together with two ammeters. OR Fig. 5.2 gives the symbol for an electronic circuit component, and Fig. 5.3 displays a circuit containing this component, an LDR and a relay.

Oct/Nov 2021

A meter used to measure the rate at which charge flows through a resistor is inserted into a circuit. What is this meter called, and in what way is it connected to the resistor?

Oct/Nov 2022

The diagram illustrates a lightning strike. Charge moves between the cloud and objects on the ground. While the lightning strike occurs, a current of $2.8 \times 10^{4}\,\text{A}$ passes between the cloud and the house for $52\,\text{ms}$. What quantity of charge flows during the lightning strike?

Oct/Nov 2025