12) Figure 20 shows a piece of apparatus called a current balance.
When the switch is closed, the part of the wire labelled X experiences a force and moves downwards.
12.1) What is the name of the effect that causes the wire X to move downwards? [1 mark]
12.2) Suggest one change you could make to the apparatus in Figure 20 that would increase the size of the force that wire X experiences. [1 mark]
Figure 21 shows how a small weight placed on the insulating bar makes the wire X go back and balance in its original position.
12.3) The wire X is 5 cm long and carries a current of 1.5 A.
The small weight causes a clockwise moment of 4.8 x 10–4 Nm.
Calculate the magnetic flux density where the wire X is positioned. Give the unit. [6 marks]
Magnetic flux density = ________________ Unit ________________