5 (a) A student has a bar magnet, a piece of iron the same size as the magnet, and some paper clips - Edexcel - GCSE Physics - Question 5 - 2018 - Paper 1

The student can investigate the effect of current size on the force of attraction using the following method:

1. Measure the initial position: The student should mark the initial position of the pointer before switching on the current in the solenoid.
2. Switch on the current: The solenoid should be energized, allowing the iron nail to be attracted.
3. Measure the position with current: The new position of the pointer should be recorded once the current is on.
4. Use an ammeter: An ammeter can be used to measure the current flowing through the solenoid.
5. Calculate the extension of the spring: The student should calculate how much the iron nail moves and the corresponding extension of the spring.
6. Repeat with different currents: This process can be repeated with varying current levels to see how it affects the force of attraction.

To calculate the energy transferred in extending the spring, we can use the formula for elastic potential energy:

$E = \frac{1}{2} k x^2$

where:

• $E$ is the energy transferred,
• $k$ is the spring constant (24 N/m),
• $x$ is the extension of the spring (0.12 m).

Now substituting the values:

$E = \frac{1}{2} \times 24 \, \text{N/m} \times (0.12 \, \text{m})^2$

Calculating this gives:

$E = \frac{1}{2} \times 24 \times 0.0144 = 0.1728 \, \text{J}$

Therefore, the energy transferred in extending the spring by 12 cm is approximately 0.17 J.