Describe the advantages and disadvantages of the heating effect of an…

The idea

When current flows through a resistor, energy is transferred to the thermal store of the resistor and its surroundings. This heating effect is useful in devices designed to produce heat, such as electric kettles, toasters, electric heaters and filament lamps, where a high-resistance element converts electrical energy into heat or light. The same effect is a disadvantage elsewhere: in connecting wires and in electronic devices it wastes energy, raises temperatures and can damage components or cause a fire risk. Devices may need cooling or thicker, lower-resistance wires to limit it. A good answer weighs both sides, naming a device where heating is wanted and a situation where it is unwanted.

What earns the marks

• States that the heating effect is useful in devices designed to produce heat, such as kettles, heaters or toasters.
• Explains that a high-resistance element converts electrical energy into thermal energy for a intended purpose.
• Identifies that unwanted heating in wires and components wastes energy and can damage them or create a fire risk.
• Describes that unwanted heating may require cooling or lower-resistance wires to limit the temperature rise.

Common mistakes and how to put them right

• Lists only advantages without any disadvantage.

  Put it right by naming a situation where heating wastes energy or damages components.

• Claims the heating effect never has a use.

  Put it right by naming a device such as a kettle or heater that relies on it.

• Confuses the heating effect with a magnetic effect.

  Put it right by describing energy transferred to the thermal store of the resistor.

Exam tips

• Give at least one named device for the advantage and one situation for the disadvantage.
• Link each point to energy transfer to or from the thermal store.
• Use the words advantage and disadvantage explicitly so each side is clear.