Question

1. What angle is needed to have the min torque?

1. 0
2. 90
3. 180
4. 270
5. 360

2. Using the right-hand rule for a wire, if the current is moving to the left, the magnetic field will be

1. Coming out of the computer screen
2. Going into the computer screen
3. Counterclockwise
4. Clockwise

3. The Earth has a magnetic field because… (mark all that apply)

1. The core is spinning
2. It has ferromagnetic materials
3. The charge is moving
4. There is a lot of heat in it

4. A torque will be produced by a magnetic field… on which plane would that happen?

1. X
2. Y
3. Z
4. All the above

Answer 1

1. The formula for torque is

Torque = rFsin(angle)

If we need torque to be minimum , sin ( angle) must be zero which is only possible if angle is either 0° or nπ.

Angle = 0°, 180°(π), 360°(2π)

Hence option A, C, E are correct.

Whereas for other options sin(angle) = 1 [ sin 90° = 1 ]

Therefore the torque will become maximum and hence those are incorrect.

2. For right hand rule, put your thumb in direction of current that is given to be left. The direction in which your finger curls is the direction of magnetic field. Hence in this case it goes inside the paper ( direction).

Therefore only option B is correct. Going into the computer screen.

All other options are incorrect.

3. The Earth's magnetic field is caused by many factors such as spin, temperature of core, inclination, electric currents due to moving charge.

Hence option A is correct, the core is spinning.

Option B is incorrect, presence of ferromagnetic material doesn't have any effect on earth's magnetic field.

Option C and D are correct because temperature and charge have influence on magnetic field.

4. The torque will be produced in a direction perpendicular to magnetic field. In general, z direction will be of torque. C option is correct.