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 current size on the force of attraction between the solenoid and the iron nail, the student can follow these steps:

1. Set up the apparatus: Connect the solenoid to a power source and place the iron nail inside or near the solenoid.
2. Measure initial position: Note the position of the iron nail when the current is off, ensuring that it is not attracted.
3. Use an ammeter: Use an ammeter to measure and record the current flowing through the solenoid as it is switched on.
4. Vary the current: Change the current in the solenoid by using a variable resistor, increasing the current in increments.
5. Measure force: For each current level, observe the force of attraction between the solenoid and the iron nail. The distance the nail moves can indicate the strength of the force.
6. Repeat measurements: Repeat the experiment multiple times for reliability, ensuring to record the current and corresponding movement of the nail each time.

To calculate the energy transferred in extending the spring, we use Hooke's Law and the formula for elastic potential energy:

1. Select and substitute: The formula for the energy transferred is given by:

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

   • $k = 24 \, \text{N/m}$ (spring constant)
   • $x = 0.12 \, \text{m}$ (extension in meters).

2. Calculate energy: Substituting in the values:

   $E = \frac{1}{2} \times 24 \, \text{N/m} \times (0.12 \, \text{m})^2 = \frac{1}{2} \times 24 \times 0.0144 = 0.1728 \, \text{J}$

3. Final result: Thus, the energy transferred in extending the spring by 12 cm is approximately $0.17 \, \text{J}$ when rounded.