Explain why iron is chosen for the core.
Explain why an electromotive force (e.m.f.) is not induced at the output when the input is a constant direct voltage.
An alternating voltage with peak value $150\,\text{V}$ is applied across the $1200$ turns of the primary coil. Fig. 9.2 shows how the induced e.m.f. $E$ across the secondary coil varies with time $t$.
Use the information in Fig. 9.2 to calculate the number of turns in the secondary coil.
State one time when the magnetic flux linking the secondary coil is a maximum.
A resistor is connected across the output terminals of the secondary coil. The mean power dissipated in the resistor is $1.2\,\text{W}$. You may assume that the alternating voltage across the resistor is the same as the varying e.m.f. $E$ shown in Fig. 9.2. Calculate the resistance of the resistor.
On Fig. 9.3, sketch the way the power $P$ dissipated in the resistor varies with time $t$ for $t = 0$ to $t = 22.5\,\text{ms}$.