An investigation is set up to study the magnetic force on a straight, current-carrying wire PQPQPQ placed in a magnetic field.
The diagram below shows the pole faces of the two magnets viewed from above, with a South pole (S\text{S}S) on the left and a North pole (N\text{N}N) on the right.
Describe the pattern and direction of the magnetic field lines that would represent a uniform magnetic field in the gap between these poles.
The wire PQPQPQ is placed horizontally in the gap, at right angles to the magnetic field. The current in the wire is 12 A12\text{ A}12 A.
Explain why a thick wire (with a large cross-sectional area) is used for this investigation instead of a very thin wire.
Explain why the wire PQPQPQ experiences a force when there is a current flowing through it.
State two ways in which the magnitude of this magnetic force can be increased.
