(a(i))[1]
Find the root-mean-square (r.m.s.) voltage, $V_{\text{r.m.s.}}$.
(a(ii))[2]
Find the period $T$.
(b)[1]
The changes in output potential difference $V$ with time $t$ for two different power supplies are shown in Fig. 9.1 and Fig. 9.2. The graphs use the same scale. State and explain whether the power dissipated in a $1.0\,\Omega$ resistor connected to each power supply is the same.
(c(i))[3]
In part (a), the power supply is linked to a transformer. The transformer’s input power is $80\,\text{W}$. A resistor is connected to the secondary coil. The r.m.s. voltage across the resistor is $120\,\text{V}$. The r.m.s. current in the secondary coil is $0.64\,\text{A}$. Calculate the efficiency of the transformer.
(c(ii))[1]
State one reason why the transformer is not $100\%$ efficient.