Fig. 8.1 shows a wire carrying a large current.
Fig. 8.1
Fig. 8.2 shows the square card viewed from above.
Fig. 8.2
On Fig. 8.2, draw three magnetic field lines that indicate the direction of the magnetic field and how its strength varies with distance from the wire.
The current in the wire increases and the direction of the current is reversed. State how these changes affect the magnetic field.
The electric starter motor in a car is switched on and off using a relay.
The relay consists of a plastic case and two flexible springy strips, X and Y, which are made of soft iron. These iron strips act as the switch when a circuit is connected between the terminals W and Z.
Fig. 7.1 shows \(\mathrm{X
Fig. 7.2 shows the equipment from Fig. 7.1 inside a magnetising coil. The magnetising coil is in series with the 12 V car battery and switch S , which is open.
Switch S is now closed.
Explain what happens to the springy iron strips X and Y .
Fig. 10.1 shows a wire that carries a current into the page. The circles on Fig. 10.1 show the pattern of the magnetic field around the wire.
Fig. 10.1
On Fig. 10.1, draw an arrow on each circle to show the direction of the magnetic field. [1]
State why the spacing of the circles increases as the distance from the wire increases.