AC Series Circuits

Any basic circuit element can be expressed in terms of its voltage and current. Ohm’s law defines that the voltage across a pure resistor is linearly proportional to the current flowing through it.

AC Resistance

The following figure shows an AC supply to a resistor. When the switch is closed, an AC voltage will cause the rise and fall of current based on the applied voltage. As the load is the resistance, both the current and voltage will reach their maximum values and fall through zero and are said to be in-phase.

FIGURE

        The following is the waveform diagram and the phasor diagram that represents the in-phase effect. The phase difference is zero and the vectors are superimposed when the voltage and current are in-phase with each other.

FIGURE

FIGURE

        As the current and voltage are in-phase, the power is always positive. The product value of current and voltage remains positive when both are either positive or negative. The average power of a complete cycle is represented by a line halfway between maximum and minimum values of the curve, as shown in the figure below.

FIGURE

        In an AC circuit, electrical resistance is called an impedance (Z), which is defined as an effective resistance of an electric circuit to alternating current and depends on the frequency of the circuit when reactive components are present. So, impedance is caused due to the combined effects of resistance and reactance.

        The average AC power is calculated using the formula below.

V_rms = root-mean-square value for voltage

R = resistance