Topic 5.4 Magnetic Fields

A beam of negative ions flows in the plane of the page through the magnetic field due to two bar magnets.

What is the direction in which the negative ions will be deflected?

M19/4/PHYSI/SPM/ENG/TZ1/XX no. 23

• Out of the page

• Into the page X

• Up the page ↑

• Down the page ↓

A horizontal wire PQ lies perpendicular to a uniform horizontal magnetic field.

A length of 0.25 m of the wire is subject to a magnetic field strength of 40 mT. A downward magnetic force of 60 mN acts on the wire.

What is the magnitude and direction of the current in the wire?

M19/4/PHYSI/SPM/ENG/TZ2/XX no. 21

• I = 6.0 ; direction = P to Q

• I = 6.0 ; direction = Q to P

• I = 0.17 ; direction = Q to P

• I = 0.17 ; direction = P to Q

Two currents of 3 A and 1 A are established in the same direction through two parallel straight wires R and S.

What is correct about the magnetic forces acting on each wire?

M19/4/PHYSI/HPM/ENG/TZ1/XX no. 18

• Both wires exert equal magnitude attractive forces on each other.

• Both wires exert equal magnitude repulsive forces on each other.

• Wire R exerts a larger magnitude attractive force on wire S.

• Wire R exerts a larger magnitude repulsive force on wire S.

A horizontal electrical cable carries a steady current out of the page. The Earth’s magnetic field exerts a force on the cable.

Which arrow shows the direction of the force on the cable due to the Earth’s magnetic field?

M19/4/PHYSI/HPM/ENG/TZ1/XX no. 19

• A

• B

• C

• D

A positively-charged particle moves parallel to a wire that carries a current upwards.

What is the direction of the magnetic force on the particle?

M17/4/PHYSI/SPM/ENG/TZ2/XX no. 21

• To the left

• To the right

• Into the page

• Out of the page

A wire carrying a current I is placed in a region of uniform magnetic field B, as shown in the diagram.

The direction of the field B is out of the page and the length of the wire is L. What is correct about the direction and magnitude of the force acting on the wire?

M16/4/PHYSI/SPM/ENG/TZ0/XX no. 21

From the options, the image at the left is for the direction and at the right is the magnitude. 

• 
• 
• 
• 

A long, straight, current-carrying wire is placed between a pair of magnets as shown. What is the direction of the force on the wire?

M15/4/PHYSI/SPM/ENG/TZ2/XX no. 21

• A

• B

• C

• D

An electron is held close to the surface of a negatively charged sphere and then released. Which describes the velocity and the acceleration of the electron after it is released?

M15/4/PHYSI/SPM/ENG/TZ2/XX no. 20

• A

• B

• C

• D

Three parallel wires, X, Y and Z, carry equal currents. The currents in X and Z are directed into the page. The current in Y is directed out of the page.

Which arrow shows the direction of the magnetic force experienced by wire Z?

M14/4/PHYSI/SPM/ENG/TZ1/XX no. 20

• $\rightarrow$ right

• $\leftarrow$ left

• ↓ down

• $\uparrow$ up

An electron is travelling in a region of uniform magnetic field. At the instant shown, the electron is moving parallel to the field direction.

The magnetic force on the electron is _______

M14/4/PHYSI/SPM/ENG/TZ2/XX no. 19

• upwards.

• downwards.

• to the right.

• zero.