Alternating current and transformers

Alternating current and transformers

1. When alternating voltages are applied to capacitors or inductors the magnitude of the current fl owing will depend upon the value of capacitance or inductance and on the frequency of the voltage. In effect, capacitors and inductors oppose the fl ow of current in much the same way as a resistor.

2. A good way of remembering leading and lagging phase relationships is to recall the word CIVIL

3. The root mean square (r.m.s.) value of an alternating voltage will produce the same amount of heat in a resistor as a direct voltage of the same magnitude.

4. Resistance and reactance combine together to make impedance. In other words, impedance is the resultant of combining resistance and reactance in the impedance triangle. Because of the quadrature relationship between voltage and current in a pure capacitor or inductor.

5. In an AC circuit the power factor is the ratio of true power to apparent power. The power factor is also the cosine of the phase angle between the supply current and supply voltage.