50 Important Basic Electrical MCQ| Objective Type Question Of Basic Electrical

Explanation:

Self-Inductance is given as

L = NΦ/I

Explanation:

The term “RMS” stands for “Root-Mean-Squared”. Most books define this as the “amount of AC power that produces the same heating effect as an equivalent DC power”

Explanation:

The R.M.S value of Square wave is given as

The Average value of square wave is given as

Hence in case of square wave, the R.M.S voltage and Average Voltage is equal to peak voltage

Explanation:

Single energy and double energy transients:

Single energy transient is the transient disturbance where only one form of energy, either electromagnetic or electrostatic is involved e.g., transient disturbance in a circuit consisting of resistor end inductor i.e., R-L circuit or a circuit consisting of resistor and capacitor i_e., R-C circuit.

Double energy transient is the transient disturbance where both electromagnetic and electrostatic energies are involved e.g., transient disturbance in a circuit consisting of resistor, inductor and capacitor i.e., R-L-C circuit.

Ques 45. The transient currents are associated with the

1. Changes in the stored energy in the inductors and capacitors
2. Impedance of the circuit
3. Applied voltage to the circuit
4. Resistance of the circuit

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Explanation:

The transient disturbances in the electrical circuit are disturbances caused by sudden switching off and on or short circuit of the circuit and sudden change in the applied voltage. The current developed in the circuit due to this disturbance is called the “transient current”. The “resultant current” in the circuit is the steady-state current with a transient current superimposed. The transient currents are found to be associated with the changes in stored energy in capacitors and inductors. Hence in a purely resistive circuit, no transient current is developed since there is no stored
energy in a resistor.

Explanation:

• When resonance occurs due to the application of the proper frequency ( fr), the energy absorbed by one reactive element is the same as that released by another reactive element within the system.
• Resonant Frequency: The frequency at which the inductive and capacitive reactance of a parallel resonant circuit are equal and the parallel impedance of a parallel resonant circuit has a power factor of unity.

Explanation:

The average value of an alternating current is expressed by that steady current which transfers across any circuit the same charge as is transferred by that alternating current at the same time.
In the case of a symmetrical alternating current (i.e., one whose two half cycles are exactly similar, whether sinusoidal or non-sinusoidal) the average value over a complete cycle is zero. Hence, in their case, the average value is obtained by adding or integrating the instantaneous value of current or voltage over one-half cycle only

But in the case of an unsymmetrical alternating current (like half-wave rectified current), the average value must always be taken over the whole
cycle.

Explanation:

The circuit containing only a pure resistance of (Say, R ohms) in the AC circuit is known as Pure Resistive AC Circuit. The inductance and capacitance do not exist in a purely resistive circuit. The Alternating current and voltage both move forward as well as backward in both the direction of the circuit. Hence, the Alternating current and voltage follows a shape of Sine wave or known as the sinusoidal waveform.

In the pure resistive circuit, the power is dissipated by the resistors and the phase of the voltage and current remains same i.e., both the voltage and current reach their maximum value at the same time.

When an AC circuit contains only resistive devices, Ohms Law, Kirchoff’s Laws, and the Power Laws can be used in exactly the same way as in DC circuits.

Explanation:

The nature of the inductor is to resist the change in current through it, therefore, the current lags behind the voltage by 90°

Explanation:

Capacitor store energy in the form of the electric field, while inductor stores energy in the form of magnetic field.They never dissipate energy, although they store energy during the one-half cycle and releases energy during another half cycle for an AC signal. So The average power consumed in an inductor and capacitor is zero over a cycle.

The resistance dissipates energy in the form of heat.