Simple a.c. circuits

In alternating current circuits, both the electromotive force (e.m.f.) and current constantly change direction and magnitude. When we plot these quantities on a graph against time, we get smooth, wave-like curves called sine waves. The e.m.f. generated by Nigeria's power stations follows this pattern, oscillating 50 times per second at 50 Hz frequency.

On your graph, the vertical axis shows the e.m.f. or current value, while the horizontal axis represents time. These sinusoidal curves help us understand how electricity behaves in our homes. Notice that in purely resistive circuits, the e.m.f. and current curves peak at exactly the same time—they are "in phase." However, in circuits containing inductors or capacitors, these curves shift apart, showing a phase difference.

Understanding these graphs lets you predict circuit behavior and solve complex problems easily.

Alternating current constantly changes direction and magnitude, rising and falling in a smooth wave pattern. The peak value is the maximum voltage or current the AC reaches at its highest point. However, what actually powers your devices is the RMS (root mean square) value, which represents the equivalent DC voltage that would produce the same power.

Think of it like this: the NEPA electricity supplied to Nigerian homes is quoted as 230V, but this is the RMS value, not the peak. The actual peak voltage reaches about 325V, which would be dangerous if continuously applied. The RMS value of approximately 0.707 times the peak value safely describes the effective power delivered to your refrigerator, air conditioner, or television.

This relationship matters because power calculations in AC circuits always use RMS values unless specifically stated otherwise.