Effective Value of Current

The effective value of current refers to the root mean square (RMS) current. It is a mathematical representation of the average value of an alternating current waveform. The RMS current is widely used in electrical engineering to determine the equivalent direct current (DC) value that would produce the same heating effect in a resistive load.

RMS Current
The RMS current is calculated by taking the square root of the average of the squares of the instantaneous current values over a complete cycle. It is defined as the value of the direct current that would produce the same amount of heat in a given resistor.

Average Current
The average current is the arithmetic mean of the instantaneous current values over a complete cycle. However, in an alternating current waveform, the instantaneous current is constantly changing direction, resulting in an average value of zero. Therefore, the average current is not an accurate representation of the current in an AC circuit.

Instantaneous Current
The instantaneous current refers to the value of current at a specific point in time. In an AC circuit, the instantaneous current continually varies in magnitude and direction as the waveform oscillates. It is characterized by a sinusoidal waveform, where the current alternates between positive and negative values.

Total Current
The total current refers to the sum of all current components in a circuit, including any DC and AC components. In AC circuits, the total current can be calculated by adding the RMS value of the AC component and the DC component.

Conclusion
The effective value of current, also known as the RMS current, is the most accurate representation of the current in an AC circuit. Unlike the average current, it takes into account both the magnitude and direction of the instantaneous current values. Therefore, option 'A' - RMS current is the correct answer.