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 $8.5A$

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

A current of $8.5 A$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 $5.2cm$.

(c) Calculate the magnetic flux density of the magnetic field between
the poles of the magnet.

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 $5.2cm$. Describe what happens to the frame if low-frequency alternating current passes through the wire.