$A$ current-carrying wire produces:

Name and state the rule to determine the direction of a force experienced by a current-carrying straight conductor placed in a magnetic field which is perpendicular to it. Name a device that uses a current-carrying conductor and a magnetic field.

$A$ device used for producing current is:

$A$ compass needle is placed near a current-carrying wire. State your observation for the following cases and give the reason for the same in each case:
$(a)$ Magnitude of electric current in the wire is increased.
$(b)$ The compass needle is displaced away from the wire.

Choose the incorrect statement from the following regarding magnetic field lines.

How does the strength of the magnetic field at the centre of a circular coil of wire depend on: $(i)$ the radius of the coil $(ii)$ the number of turns of wire in the coil $(iii)$ the strength of the current flowing in the coil?