1. What differentiates Alternating Current (AC) from Direct Current (DC)?
Answer:
Explanation:
The primary difference is that AC changes its direction periodically while DC flows in a constant direction.
2. The standard frequency of AC in most countries is:
Answer:
Explanation:
In most countries, the standard frequency of AC is 50 Hz, though some, like the USA, use 60 Hz.
3. The average value of AC over one complete cycle is:
Answer:
Explanation:
Over one complete cycle, the positive half cancels out the negative half, resulting in an average value of zero.
4. The effective or RMS value of an AC is:
Answer:
Explanation:
RMS (Root Mean Square) value is approximately 0.707 times the peak value for a sinusoidal AC.
5. In a purely resistive AC circuit, the phase difference between current and voltage is:
Answer:
Explanation:
In a purely resistive circuit, the current and voltage are in phase, resulting in a phase difference of 0 degrees.
6. In an AC circuit with only capacitance, the current leads the voltage by:
Answer:
Explanation:
In a purely capacitive circuit, the current leads the voltage by a phase difference of 90 degrees.
7. Which device allows AC to pass but blocks DC?
Answer:
Explanation:
A capacitor blocks DC and allows AC to pass through.
8. The impedance in an LCR circuit is given by:
Answer:
Explanation:
Impedance, Z, in an LCR circuit is given by Z = √(R^2 + (XL – XC)^2).
9. In an AC circuit with only inductance, the voltage leads the current by:
Answer:
Explanation:
In a purely inductive circuit, the voltage leads the current by a phase difference of 90 degrees.
10. Power factor in an AC circuit is defined as:
Answer:
Explanation:
Power factor is the cosine of the phase difference, defined as the ratio of resistance to impedance, i.e., cos(Φ) = R/Z.
11. The power consumed in a purely capacitive circuit is:
Answer:
Explanation:
In a purely capacitive circuit, the power consumed is zero as the phase difference between current and voltage is 90 degrees.
12. In a series LCR circuit at resonance, the impedance is:
Answer:
Explanation:
At resonance in a series LCR circuit, XL = XC, so impedance Z equals the resistance R.
13. Resonance in an AC circuit means:
Answer:
Explanation:
At resonance, the impedance is minimum, and current is maximum in a series LCR circuit.
14. The unit of reactance is:
Answer:
Explanation:
Reactance (both capacitive and inductive) is measured in Ohms.
15. Which of the following is not a type of transformer?
Answer:
Explanation:
There's no such thing as a 'step-side' transformer. Common types include step-up, step-down, and power transformers.
16. In an AC generator, the produced EMF is directly proportional to:
Answer:
Explanation:
The induced EMF in an AC generator is directly proportional to the speed of rotation and the number of turns in the coil.
17. In a pure inductance, the power factor is:
Answer:
Explanation:
For a purely inductive circuit, the power factor is zero, as the phase difference between current and voltage is 90 degrees.
18. In a transformer, the number of turns in the primary coil compared to the secondary coil determines:
Answer:
Explanation:
In a transformer, the ratio of the number of turns in the primary coil to the secondary coil determines whether the voltage is stepped up or stepped down.
19. The phenomenon of a current in the primary coil inducing a current in the secondary coil without any direct connection is called:
Answer:
Explanation:
Mutual induction is the phenomenon where a change in current in one coil induces a voltage in a nearby coil.
20. Choke in a tube light is essentially a:
Answer:
Explanation:
The choke in a tube light is essentially an inductor used to regulate the current in the circuit.