Physics 9702 · AS & A Level · Characteristics of alternating currents
Characteristics of alternating currents — practice question
As shown in Fig. 6.1, an alternating current supply is connected in series with a resistor $R$. The current $I$ in the resistor, measured in amps, changes with time $t$ (measured in seconds) according to $I = 9.9\sin(380t)$.
(a(i))[2]
Determine the frequency of the current in resistor $R$.
(a(ii))[2]
Determine the r.m.s. current for the current in resistor $R$.
(b)[2]
To avoid overheating, the mean power dissipated in resistor $R$ must stay below $400\,\text{W}$. Calculate the minimum resistance of $R$.
Worked solution & mark scheme
This 6-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Applies $2\pi f = 380$” …