This diagram shows a view from above of two long, parallel strips of aluminium foil,$A$ and $B$, carrying a current downwards into the paper.

(a) On a copy of the diagram, draw the magnetic field around and between the two strips.

This diagram shows a view from above of two long, parallel strips of aluminium foil, A and B, carrying a current downwards into the paper.

(b) State and explain the direction of the forces caused by the current in the strips.

This diagram shows a wire $XY$ that carries a constant direct current. Plotting compass $R$, placed alongside the wire, points due north. Compass $P$ is placed below the wire and compass $Q$ is placed above the wire.

(a) State the direction of the current in the wire.

This diagram shows a wire $XY$ that carries a constant direct current. Plotting compass $R,$ placed alongside the wire, points due north. Compass $P$ is placed below the wire and compass $Q$ is placed above the wire.

(b) State in which direction compass P points.

This diagram shows a wire $XY$ that carries a constant direct current. Plotting compass $R,$ placed alongside the wire, points due north. Compass $P$ is placed below the wire and compass $Q$ is placed above the wire.

 State in which direction compass Q points if the current in
the wire is reversed.

This diagram shows a rectangular metal frame$PQRS$ placed in a uniform magnetic field.

The magnetic flux density is $4.5\times {10}^{-3}T$ and the current in the metal frame is $2.5A$

(a) Calculate the force experienced by side $PQ$ of the frame.

This diagram shows a rectangular metal frame$PQRS$ placed in a uniform magnetic field.

The magnetic flux density is $4.5\times {10}^{-3}T$ and the current in the metal frame is $2.5A$

(b) Suggest why side QR does not experience a force.

This diagram shows a rectangular metal frame$PQRS$ placed in a uniform magnetic field.

The magnetic flux density is $4.5\times {10}^{-3}T$ and the current in the metal frame is $2.5A$

(c) Describe the motion of the frame immediately after the
current in the frame is switched on.

This diagram shows a rectangular metal frame$PQRS$ placed in a uniform magnetic field.

The magnetic flux density is $4.5\times {10}^{-3}T$ and the current in the metal frame is $2.5A$

(d) Calculate the maximum torque (moment) exerted about an
axis parallel to side$PQ$ .