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$PQ$ .

This diagram shows a current-carrying wire frame placed between a pair of magnets on a yoke. A pointer is attached to the wire.

A current of $8.5 A$ in the wire causes the pointer to move vertically upwards. A small paper tape is attached to the pointer and the current is adjusted until the weight of the paper tape causes the pointer to return to its initial position (with no current and no paper tape). The mass of the paper tape is $60 mg.$ The section of the wire between the poles of the magnetic has a length of $5.2cm$.

(a) State the direction of the magnetic field.

This diagram shows a current-carrying wire frame placed between a pair of magnets on a yoke. A pointer is attached to the wire.

A current of $8.5 A$ in the wire causes the pointer to move vertically upwards. A small paper tape is attached to the pointer and the current is adjusted until the weight of the paper tape causes the pointer to return to its initial position (with no current and no paper tape). The mass of the paper tape is $60 mg.$ The section of the wire between the poles of the magnetic has a length of $5.2cm$. Calculate the force on the wire due to the magnetic field when it Carries a current of $8.5A$