Understanding Alternating Current (AC)

Front

Understand the role of reactance within AC circuits.

Back

Reactance is the opposition to the flow of AC caused by inductors and capacitors, affecting the phase and magnitude of the current.

Front

AC generation involves permanent magnets creating a steady magnetic field.

Back

A rotating coil (armature) moves between the poles of the magnets, inducing EMF (voltage) as the magnetic flux changes according to Faraday's law. Continuous rotation results in a sinusoidal change in flux, producing alternating current (AC). The frequency of AC depends on the rotation speed and the number of poles in a multipole design.

Front

AC is used in national grid systems because it can be easily transformed to high or low voltage levels.

Back

AC current is versatile and can be adjusted to different voltage levels, making it suitable for national grid systems.

Front

A sinusoidal waveform representing the e.m.f. generated by an alternator plotted against time. The graph shows voltage (V) versus angle (degrees), with one complete revolution marked.

Back

The sinusoidal waveform represents the alternating nature of the e.m.f. generated by an alternator. It oscillates between positive and negative values, completing one cycle in 360°.

Front

Positive peak in AC signals

Back

The positive peak is the maximum positive value of voltage or current in a sinusoidal cycle.

Front

AC signal representation

Back

AC signals are represented as sinusoidal waves, showing periodic oscillations of voltage or current.

Front

Formula to calculate r.m.s. voltage (Vrms) in terms of peak voltage (Vpeak).

Back

Front

The importance of radians in the calculation.

Back

The calculation of instantaneous voltage should be performed in radians for accurate results.

Front

The relationship between frequency and time in a sine wave.

Back

Frequency and time are inversely related; higher frequency results in shorter time periods for each cycle.

Front

Formula to find peak voltage.

Back