Define the tesla.

1. (a)Define the tesla.[2]
2. (b)(i)A stiff metal wire is used to form a rectangular frame measuring 8.0cm x 6.0 cm. The frame is open at the top, and is suspended from a sensitive newton meter, as shown in [Figure 8.1]. The open ends of the frame are connected to a power supply so that there is a current of 5.0A in the frame in the direction indicated in [Figure 8.1]. The frame is slowly lowered into a uniform magnetic field of flux density B so that all of side PQ is in the field. The magnetic field lines are horizontal and at an angle of 50° to PQ, as shown in [Figure 8.2]. When side PQ of the frame first enters the magnetic field, the reading on the newton meter changes by 1.0mN. Determine the magnetic flux density B, in mT.[2]
3. (b)(ii)State, with a reason, whether the change in the reading on the newton meter is an increase or a decrease.[1]
4. (b)(iii)The frame is lowered further so that the vertical sides start to enter the magnetic field. Suggest what effect this will have on the frame.[1]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.