3 (a) A student has a bar magnet, a piece of iron the same size as the magnet, and some paper clips - Edexcel - GCSE Physics Combined Science - Question 3 - 2018 - Paper 1

To investigate the effect of the current size in the solenoid on the force of attraction, the student should follow these steps:

1. Set Up the Apparatus: Connect the solenoid to a power source and place the iron nail close to the solenoid without touching it.

2. Initial Measurement: Measure the initial position of the iron nail when the current is off. This creates a baseline for measurements.

3. Current Variation: Turn on the current and gradually increase it while noting the current values with an ammeter. Measure how far the nail moves towards the solenoid with each increment of current.

4. Force Calculation: Use the force of attraction formula to compute the force based on measurements taken at each current level, relating extension of the nail's movement to the varying current sizes.

5. Repeat for Accuracy: Repeat the experiment with different current levels to obtain reliable data, ensuring consistency in measuring the movement of the iron nail.

To calculate the energy transferred in extending the spring, we will use the following equation:

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

Where:

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

Substituting these values into the equation:

$E = \frac{1}{2} \times 24 \times (0.12)^2$

Calculating this gives:

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

Rounding off, the energy transferred is approximately 0.17 J.