Electrical quantities

When a camera flash is operated, a charge of $1.5\,\text{C}$ passes through the flash-tube in $0.0030\,\text{s}$. The average potential difference across the flash-tube is $3600\,\text{V}$. Calculate the electrical energy delivered to the flash-tube and the average power delivered.

May/June 2015

Electrical power is sent through cables over long distances at very high voltages. What effects result from using a high-voltage transmission system?

May/June 2016

Fig. 6.1 illustrates a $240\,\text{V}$ a.c. mains supply linked to a television and two lamps. Under normal operation, each lamp receives $40\,\text{W}$ of power, while the television receives $120\,\text{W}$.

May/June 2017

$V$ represents potential difference, $I$ represents current, $R$ stands for resistance, and $t$ denotes time. Which expression has the units of energy?

May/June 2018

When a filament lamp is connected to a $12\,\text{V}$ supply, its power input is $20\,\text{W}$.

May/June 2021

Electrical power is carried by cables over long distances at very high voltages. What effects does a high-voltage transmission system have?

May/June 2022

A current of $1.5\,\text{A}$ flows through a $4.0\,\Omega$ resistor. What amount of energy is converted from electrical energy to thermal energy in $1.0$ minute?

May/June 2025

Which row correctly identifies an electrical conductor and an insulator?

Oct/Nov 2015

An immersion heater has the marking $24\,\text{V}$, $120\,\text{W}$. What current flows through the heater when it is attached to a $24\,\text{V}$ supply?

Oct/Nov 2015

A television studio spotlight is operating at full brightness. The bulb inside the spotlight is supplied with 230 V, and the current through the lamp filament is 27 A.

Oct/Nov 2015

A $60\,\text{W}$ filament lamp is supplied from the $240\,\text{V}$ mains electricity supply.

Oct/Nov 2019

Fig. 10.1 illustrates a wire with length $l$ and cross-sectional area $A$. Fig. 10.2 illustrates a solid cube of metal W with side $1.0\,\text{cm}$. Fig. 10.3 illustrates a circuit made up of a $1.2\,\text{V}$ cell, a $9.6\,\Omega$ resistor and a $1.0\,\text{m}$ length of wire. Fig. 10.4 illustrates the oscilloscope screen.

Oct/Nov 2020

An electromagnet is used to sort magnetic objects from non-magnetic ones. Fig. 6.1 shows the electromagnet hanging from the arm of a crane.

Oct/Nov 2022

Which material is an electrical conductor at room temperature?

Oct/Nov 2025

A cardboard tube has two wires, P and Q, attached to its ends. Within the tube, wire P and wire Q are connected to two resistors. The potential difference (p.d.) between wire P and wire Q is $9.0\text{ V}$ and the current in the wires is $0.75\text{ A}$. Which combination of resistors is inside the tube?

Oct/Nov 2025

The circuit contains a battery with e.m.f. 9.0 V, a switch, resistor P, an ammeter, a 4.0 Ω resistor and a voltmeter. Fig. 6.1 gives the circuit diagram. Resistor P is a cylinder of length l, formed from conducting modelling clay. Fig. 6.2 displays resistor P. P has a resistance of 8.0 Ω. The conducting modelling clay from resistor P is then remoulded to produce a second cylindrical resistor with the same volume as resistor P but with a length $\frac{l}{2}$. Fig. 6.3 displays the remoulded resistor.

Oct/Nov 2025

An insulating rod is plastic and is uncharged at the start. It is rubbed with a cloth, after which it acquires a negative charge. A light ball has a thin conducting surface and hangs from the ceiling on an insulating thread. The ball has no charge. When the negatively charged rod is moved close to the ball, Fig. 7.1 shows the ball being pulled towards the rod by a force. Diagram labels: ceiling, insulating thread, light ball, negatively charged rod, direction of force.

Oct/Nov 2025

An electric car is propelled by a direct current (d.c.) motor, and this motor is supplied by a direct current power supply. Fig. 6.1 shows the motor circuit. Point P is located in the circuit between the motor and the positive terminal of the power supply. In the circuit diagram, point P appears to the left of the motor. Over a time interval of 120 s, the current in the circuit at point P is 41 A.

Oct/Nov 2025

A solar cell is a device that produces electrical power when light shines on it. You are given a solar cell connected to a fixed resistor, as in the incomplete circuit shown in Fig. 4.1. The power of the cell can be determined from the equation: power = current \times voltage. Extra apparatus available includes a lamp connected to a power supply, a metre rule, a voltmeter, an ammeter and connecting leads. Any other equipment normally found in a school laboratory may also be used.

Oct/Nov 2025

A student is studying a light dependent resistor (LDR). The student sets up a series circuit made up of a power supply, the LDR, a 560 Ω resistor and a switch. Fig. 1.1 presents circuit symbols for: resistor, variable resistor, resistor with bands, thermistor, cell/power supply terminals, LDR, switch, diode and LED.

Oct/Nov 2025