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

Characteristics of alternating currents — practice question

A carrier wave with sinusoidal form keeps a constant amplitude and has a frequency of $1.2\,\text{MHz}$. It is then modulated by a signal wave so that a $1.0\,\text{V}$ displacement in the signal wave produces a $25\,\text{kHz}$ shift in frequency. The signal wave has frequency $8.0\,\text{kHz}$ and amplitude $2.0\,\text{V}$.
(a(i))[1]

State the modulation type used for the carrier wave.

(a(ii)-1)[3]

For this modulated carrier wave, determine the change, if any, in its amplitude.

(a(ii)-2)[3]

For this modulated carrier wave, determine the change, if any, in its frequency.

(a(ii).1)[2]

For this modulated carrier wave, determine the change, if any, in its amplitude.

(a(ii).2)[1]

For this modulated carrier wave, determine the change, if any, in its frequency.

(b(i))[2]

For this transmission, determine the wavelength, in km, of the carrier wave.

(b(ii))[1]

For this transmission, determine the bandwidth.

(b(iii))[1]

For this transmission, determine the frequency of the audio signal.

Worked solution & mark scheme

This 14-mark question has a full step-by-step worked solution and mark scheme. One marking point: “FM (frequency modulation)” …

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