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1.

(a)

A sinusoidal alternating voltage has a peak value of 12 V and a frequency of 50 Hz.  Calculate its time period.

2

 

 

 

 

 

 

 

 

 

(b)

Write an equation that would allow you to work out the instantaneous voltages for a time, t, after the voltage went through the 0 point.  Include numerical values in the terms.

2

 

 

 

 

 

 

 

(c)

Use your equation to work out instantaneous values for the voltage at these times.  Show your working out.

 

 

 

(i)

4 ms

2

 

 

 

 

 

 

 

 

(ii)

7 ms

2

 

 

 

 

 

 

 

 

(iii)

18 ms

2

 

 

 

 

 

 

 

 

 

 

 

2.

The diagram shows a CRO screen:

 

 

The voltage gain is set at 0.2 V cm-1 and the time base is set at 10 ms cm-1.

 

 

 

(a)

Calculate:

 

 

 

(i)

The peak to peak voltage;

2

 

 

 

 

 

 

 

 

 

 

 

(ii)

The RMS voltage;

2

 

 

 

 

 

 

 

 

 

 

 

(iii)

The frequency.

2

 

 

 

 

 

 

 

 

 

 

(b)

The signal generator producing the sinusoidal wave is now adjusted so that it makes a triangular wave of exactly the same peak voltage and frequency.

 

2

 

 

(i)

Work out the new RMS voltage.

 

 

 

 

 

 

 

 

 

 

3

An alternating voltage is represented by the equation .

Work out:

 

 

(a)

The maximum value of the voltage:

1

 

 

 

 

 

 

 

(b)

The frequency

2

 

 

 

 

 

 

 

 

 

 

(c)

The periodic time

1

 

 

 

 

 

 

 

(d)

What is the angular velocity of the phasor representing this waveform?

2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

4.

The instantaneous voltage of two alternating voltages are given by these two equations:

 

 

 

 

 

(a)

Sketch a phasor diagram for the two voltage vectors.

4

 

 

 

 

(b)

By accurate drawing or resolution of vectors, obtain expressions for:

7

 

 

(i)

V1 + V2

 

 

 

(ii)

V1 V2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Answers