ISCET Electronic Components & Circuit Analysis 3 — Questions and Answers
Question 1: When a silicon diode is forward biased, the typical voltage drop across it is approximately:
- 0.1 V
- 0.3 V
- 0.7 V (Correct answer)
- 1.2 V
Correct answer: 0.7 V
Silicon diodes have a forward voltage drop of approximately 0.7 V, while germanium diodes drop about 0.3 V.
Question 2: In a Wheatstone bridge circuit, the bridge is said to be balanced when:
- All four resistors are equal
- The galvanometer reads zero current (Correct answer)
- The supply voltage equals the output voltage
- Two adjacent resistors are equal
Correct answer: The galvanometer reads zero current
A Wheatstone bridge is balanced when the ratio R1/R2 = R3/R4, resulting in zero current through the galvanometer.
Question 3: What does the 'Q factor' of a resonant circuit indicate?
- The ratio of reactance to resistance (Correct answer)
- The total power dissipated
- The cutoff frequency
- The impedance at resonance
Correct answer: The ratio of reactance to resistance
Q factor (quality factor) is the ratio of reactance to resistance, indicating the selectivity and efficiency of a resonant circuit.
Question 4: A full-wave rectifier using a center-tapped transformer produces a ripple frequency of:
- Equal to the input frequency
- Half the input frequency
- Twice the input frequency (Correct answer)
- Four times the input frequency
Correct answer: Twice the input frequency
A full-wave rectifier produces output pulses during both half-cycles, resulting in a ripple frequency twice the input AC frequency.
Question 5: In a common-collector (emitter follower) amplifier, the voltage gain is approximately:
- Very high (>100)
- Equal to hFE
- Slightly less than 1 (Correct answer)
- Zero
Correct answer: Slightly less than 1
The emitter follower has a voltage gain just under 1, but provides high current gain and acts as an impedance transformer.
Question 6: What is the primary purpose of a snubber circuit used with switching components?
- Increase switching speed
- Suppress voltage transients and ringing (Correct answer)
- Reduce conduction losses
- Filter harmonics from the output
Correct answer: Suppress voltage transients and ringing
Snubber circuits (typically RC networks) absorb the energy of voltage spikes caused by rapid switching of inductive loads.
Question 7: Which parameter of a capacitor determines how much charge it can store per unit voltage?
- Dielectric strength
- Capacitance value in farads (Correct answer)
- Equivalent series resistance (ESR)
- Working voltage rating
Correct answer: Capacitance value in farads
Capacitance (C = Q/V) directly defines the charge stored per volt; larger capacitance stores more charge at the same voltage.
ISCET Electronic Components & Circuit Analysis 3
When a silicon diode is forward biased, the typical voltage drop across it is approximately: