Edexcel iGCSE Physics (4PH1) 6.4 Electromagnetic Induction Exam Style Question Paper 1B - New Syllabus

(a)(i) Correct Answer: \( \boxed{\mathrm{B\ (elastic)}} \) [1 mark]

Adding the weight stretches the spring, so the energy in the elastic store of the spring increases.

For a spring, the elastic energy store can be related to its extension by \(E_{\mathrm{elastic}}=\dfrac{1}{2}kx^2\), where \(k\) is the spring constant and \(x\) is the extension.

(a)(ii) Energy transfers until the spring stops vibrating [6 marks]

• When the spring is released, its elastic energy store decreases as the spring moves upwards.
• Energy is transferred to the kinetic store of the weight and spring as they accelerate upwards.
• The gravitational potential energy store increases as the weight moves upwards.
• At the highest point, the motion reverses and the weight moves downwards, so gravitational potential energy is transferred to the kinetic store.
• As the spring moves downwards again, energy is transferred mechanically back into the elastic store of the spring.
• The amplitude of the vibrations decreases because energy is transferred to the thermal store of the spring and surroundings, mainly due to friction and air resistance.

Eventually, the vibrations stop and the energy initially stored in the spring has been transferred mainly to the thermal store of the spring and its surroundings.

Key principle: Energy is not destroyed. It is transferred between different energy stores.

(b)(i) Advantage of the new shock absorber [1 mark]

Correct Answer: \( \boxed{\mathrm{B\ it\ increases\ the\ efficiency\ of\ the\ motorcycle}} \)

Some energy that would otherwise be wasted is recovered and converted into useful electrical energy, so the overall efficiency increases.

(b)(ii) Generating electricity [3 marks]

• The magnets move through the coil when the shock absorber moves.
• The moving magnets cause the coil to cut magnetic field lines, so the magnetic field through the coil changes.
• An induced voltage is produced in the coil, which can cause a current to flow and generate electrical energy.

This is an example of electromagnetic induction.

(b)(iii) Why more electricity is generated on Road X [3 marks]

• Road X has a rougher surface, so there are more frequent and/or larger bumps.
• The shock absorber therefore compresses and expands more frequently and/or by a greater amount.
• The magnets move through the coil more frequently and/or over a greater distance, producing a larger or more frequent induced voltage and therefore more electrical energy.

The key idea is that greater movement of the magnets through the coil produces a greater amount of electromagnetic induction.

Final Answer: Road X causes more movement of the magnets through the coil, so the magnetic field through the coil changes more frequently and/or by a greater amount. This produces more induced voltage and therefore more electricity.