Physics 9702 · AS & A Level · Characteristics of alternating currents

Characteristics of alternating currents — practice question

(a)[2]

What does the root-mean-square (r.m.s.) value of an alternating voltage mean?

(b)

An alternating voltage $V$ is given by $V = 220\sin(120\pi t)$, where $V$ is measured in volts and $t$ is in seconds. For this alternating voltage, determine:

(b(i))[1]

the maximum voltage.

(b(ii))[1]

the root-mean-square value of the voltage.

(b(iii))[1]

the frequency value.

(c)[2]

In part (b), the alternating voltage is connected across a resistor, and the resistor’s mean power output is $1.5\,\text{kW}$. Calculate the resistance of the resistor.

Worked solution & mark scheme

This 7-mark question has a full step-by-step worked solution and mark scheme. One marking point: r.m.s. voltage gives same power as a steady voltage

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