Figure 8 shows two magnets with their N poles facing each other - Edexcel - GCSE Physics - Question 5 - 2023 - Paper 2

The forces acting on the upper magnet involve interactions between the magnetic fields of the two magnets.

1. The upper magnet experiences a repulsive force due to the magnetic field of the lower magnet. This is a result of the like poles (N-N) repelling each other, pushing the upper magnet upwards.

2. The weight of the upper magnet acts downwards, pulling it towards the ground.

3. In equilibrium, the upward force due to repulsion and the downward gravitational force are equal and opposite, meaning the magnets are balanced in their position.

The direction of the force on the wire is perpendicular to both the magnetic field and the direction of current. Using the right-hand rule, if the current is flowing to the right while the magnetic field lines go from N to S, the force on the wire will be upwards.

The direction of the force on the magnet will be downwards, due to the interaction with the current-carrying wire above it, where the magnetic fields interact.

Using the formula for the force on a current-carrying conductor within a magnetic field, we have:

$F = B I L$

Where:

• $F = 0.15 \, \text{N}$ (force on the wire)
• $B = 0.50 \, \text{T}$ (magnetic flux density)
• $I = 2.7 \, \text{A}$ (current in the wire)

Rearranging the formula to solve for the length $L$, we get:

$L = \frac{F}{B I}$

Substituting the values into the equation gives:

$L = \frac{0.15}{0.50 \times 2.7} = 0.11 \, \text{m}$

Thus, the length of the wire in the magnetic field is 0.11 m.