Apparatus:

Top pan electric balance, shaped length of copper wire, clamp-stand etc., digital multimeter set on 10A dc, rheostat, 6V PSU, wires, push-to-make switch, protractor, ruler.

Diagrams:

Side view (left) view from above (right)

Set up procedure:

Clamp the shaped piece of copper wire so that its lower horizontal section lies between the poles of a set of magnadur magnets on the pan of the top-pan balance as shown in the diagrams above. Connect the copper wire to a circuit containing the push-to-make switch, rheostat, ammeter and power supply. You will use the rheostat to control the current, I through the copper wire.

Investigations:

According to theory, the force,exerted on a straight conductor of length,carrying a current,is given by

where

= magnetic flux density (a measure of the strength of the magnetic field)

= the angle between the conductor and the field direction (90̊ in the above diagrams).

With your apparatus investigate how well the above formula describes how the force exerted on the wire varies with:

(a) the current flowing,

(b) the sine of the anglebetween the horizontal wire and the field direction.