Alternating currents

You will be able to

• Determine the period, frequency and peak value of an alternating p.d. from an oscilloscope trace.
• Explain that the mean power in a resistor is half the peak power, ½I₀²R, for a sinusoidal current.
• Calculate root-mean-square values using Vᵣₘₛ = V₀ / √2 and Iᵣₘₛ = I₀ / √2, and explain them as the equivalent d.c. values.

You will be able to

• Distinguish graphically between half-wave and full-wave rectification.
• Explain the use of a bridge rectifier of four diodes for full-wave rectification, stating which diodes conduct in each half-cycle.
• Explain the smoothing effect of a capacitor, and the effect of the time constant RC on the ripple.