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

The upper magnet experiences several forces:

1. Magnetic Field Interaction: The magnetic field of the lower magnet interacts with the magnetic field of the upper magnet, resulting in magnetic repulsion since both N poles are facing each other.

2. Repulsive Force: The repulsive force acts upwards on the upper magnet due to the interaction of like poles.

3. Gravitational Force: The weight of the upper magnet acts downwards, pulling it toward the lower magnet.

4. Equilibrium: The forces are balanced if the upward repulsive force is equal to the downward gravitational force, leading to the upper magnet floating stably in the air.

The direction of the force on the wire is perpendicular to both the magnetic field and the direction of the current. If the current flows in a certain direction, use the right-hand rule to determine that direction.

The force on the magnet acts in the opposite direction to the force on the wire, meaning if the wire experiences a force in one direction, the magnet experiences a force in the opposite direction due to Newton's Third Law of Motion.

To find the length of the wire in the magnetic field, use the equation:

$F = BIL$

Where:

• $F$ is the force on the wire (0.15 N)
• $B$ is the magnetic flux density (0.50 T)
• $I$ is the current (2.7 A)

Rearranging the equation gives:

$L = \frac{F}{BI}$

Substituting the values:

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

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