H Exp – Electricity and Electronics 08 – Alternating current – peak and r.m.s.values

Aim – To establish a relationship between peak and equivalent direct (r.m.s.) values of voltage.

Instructions

▪ Switch on the left hand lamp.
▪ Adjust the a.c. voltage to give a peak alternating voltage of 1 V (peak to peak of 2 V).
▪ Leave this circuit switched on.
▪ Switch on the right hand circuit.
▪ Adjust the d.c. voltage so that the lamp is the same brightness as the left hand lamp.
▪ Measure the deflection of the spot on the oscilloscope. This gives a measure of the direct voltage across the lamp.
▪ Repeat the measurements for a.c. peak voltages of 2 V, 3 V, and 4 V.
▪ Plot a graph of direct voltage against peak a.c. voltage.
▪ Determine the gradient of the graph.
▪ State the relationship between V_d.c.d.c. and V_peak using the value obtained from the gradient of the graph.

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