What type of force exists between the two magnets in Figure 4? (b) State two factors that affect the size of the force between the magnets. (c) Draw the magnetic field pattern between the two magnets.

$$V_s = 240 \text{ V} \times \frac{100}{1000}$$ $$V_s = 240 \text{ V} \times \frac{1}{10}$$ $$V_s = 24 \text{ V}$$

The output voltage is $\boxed{24 \text{ V}}$.

(ii) Calculate the current in the primary coil ($I_p$).
Since the efficiency of the transformer is 100%, the input power equals the output power ($P_p = P_s$).

$$V_p I_p = V_s I_s$$

$$I_p = \frac{48 \text{ W}}{240 \text{ V}}$$ $$I_p = 0.2 \text{ A}$$

The current in the primary coil is $\boxed{0.2 \text{ A}}$.

(iii) Calculate the power of the radio set ($P_s$).
The power of the radio set is the output power of the transformer.

$$P_s = V_s I_s$$

$$P_s = 48 \text{ W}$$

The power of the radio set is $\boxed{48 \text{ W}}$.

(iv) State two sources of energy losses in a transformer.

• Eddy current losses in the core.
• Hysteresis losses in the core.
• Copper losses (resistance of the windings).
• Magnetic flux leakage.

5.
Figure 5 shows a solenoid XY with a current flowing in the direction indicated.

(i) Copy the diagram and indicate the magnetic flux pattern around the solenoid.
(Drawing the magnetic flux pattern)
Using the right-hand grip rule: If you curl the fingers of your right hand in the direction of the current (which goes over the top of the solenoid from right to left), your thumb points to the left. This indicates that end X is the North pole and end Y is the South pole.
Draw magnetic field lines emerging from end X (North pole) and entering end Y (South pole) outside the solenoid. Inside the solenoid, the field lines should be straight and parallel, directed from Y to X.

(ii) State the polarity of the ends X and Y of the solenoid.

• End X is the North pole.
• End Y is the South pole.