Basic Electrical & Electronics Question Bank

The number of complete cycles an AC signal makes in one second. Measured in Hertz (Hz).

Represents the power factor of an AC circuit. It lies between 0 and 1, where 1 indicates purely resistive load and 0 indicates purely reactive load.

They have both a phase (positive and negative cycles) and a neutral point (zero voltage reference).

230 Volts (V) and 50 Hertz (Hz) are the standard values of voltage and frequency for electricity systems in India. These values are used to power homes and businesses.

The time taken for one complete cycle of an AC wave. It is the inverse of frequency.

The unit used to express frequency in cycles per second. One Hertz (Hz) is equal to one complete cycle per second.

When waveform-1 starts from the origin and waveform-2 starts from π/2, waveform-1 is leading waveform-2. They are out of phase by a phase angle of π/2 radians or 90 degrees. This means waveform-1 reaches its peak value earlier than waveform-2.

The average value of a set of currents is calculated by summing up all the currents and dividing by the number of currents. In this case, the average current is 6A.

A transformer is an electrical device that uses electromagnetic induction to change the voltage of an alternating current (AC) without changing the frequency. It either steps up (increases) or steps down (decreases) the voltage depending on its winding ratio.

The secondary voltage is determined by the primary voltage and the turn ratio. In this case, the secondary voltage is 12000 V. It is calculated as the product of the primary voltage and the turn ratio.

Transformer cores are laminated to reduce eddy current losses and hysteresis losses. Lamination creates thin layers of iron separated by insulating material, which disrupts the flow of eddy currents and reduces hysteresis loss.

Only frequency remains constant in an ordinary transformer. The voltage, current, and power are all transformed in proportion to the turn ratio of the windings.

In an ideal transformer, no energy loss occurs. The windings are perfectly coupled, and there is no core loss or winding resistance. This means all the magnetic flux generated by the primary winding links with the secondary winding, resulting in maximum efficiency.

The core of a transformer is typically made of iron or a ferromagnetic material with high permeability. This allows it to efficiently channel the magnetic flux generated by the windings.

The stator is the stationary part of an electric motor. It generates a rotating magnetic field that interacts with the rotor, causing it to spin.

A DC motor uses brushes and a commutator for powering the rotor. The commutator is a split ring that reverses the current flow through the rotor windings every half cycle, switching the magnetic poles and causing continuous rotation.

The direction of rotation in a DC motor can be determined using Fleming's right-hand rule. According to this rule, if the thumb, index finger, and middle finger of the right hand are extended perpendicular to each other, the thumb points in the direction of the force (rotation), the index finger points in the direction of the magnetic field, and the middle finger points in the direction of the current.

Hysteresis loss is a type of energy loss in a magnetic material. It is related to the magnetic history of the material, as energy is lost during the process of magnetization and demagnetization. This loss is directly proportional to the frequency of the magnetic field.