Electrical FundamentalsRadio Telephony — DGCA CPL practice questions
Question 1 of 17
The unit of electrical resistance is the:
All 17 questions — Electrical Fundamentals
Radio Telephony · DGCA CPL. The correct option is marked on each.
Q1. The unit of electrical resistance is the:
- A.Volt
- B.Ampere
- C.Ohm✓
- D.Watt
Why: Resistance — ohm (Ω). Volt = voltage, ampere = current, watt = power.
Q2. One ampere is a flow of charge of:
- A.One volt per second
- B.One coulomb per second✓
- C.One ohm per second
- D.One joule per second
Why: 1 A = 1 coulomb of charge per second.
Q3. A 24 V supply across a 6 Ω resistor draws:
- A.2 A
- B.4 A✓
- C.6 A
- D.144 A
Why: I = V/R = 24/6 = 4 A.
Q4. The power dissipated by 4 A through 14 Ω is:
- A.56 W
- B.224 W✓
- C.3.5 W
- D.784 W
Why: P = I²R = 4² × 14 = 16 × 14 = 224 W.
Q5. For a sine wave, the RMS value is:
- A.1.414 × peak
- B.0.707 × peak✓
- C.Equal to peak
- D.Twice peak
Why: RMS = 0.707 × peak (and peak = 1.414 × RMS).
Q6. A radio-frequency signal is a form of:
- A.Alternating current✓
- B.Direct current
- C.Static charge
- D.Resistance
Why: lternating current. Radio signals are AC — oscillating at the carrier frequency.
Q7. Typical aircraft AC power is:
- A.230 V 50 Hz
- B.115 V 400 Hz✓
- C.12 V DC
- D.28 V 60 Hz
Why: Aircraft use 115 V AC at 400 Hz (and 28 V DC); 400 Hz allows lighter components.
Q8. Resistance of a wire increases when it is:
- A.Shorter and thicker
- B.Longer, thinner and hotter✓
- C.Made of silver
- D.Cooled
Why: Resistance rises with length and temperature, falls with cross-sectional area.
Q9. Two 10 Ω resistors in series give a total of:
- A.5 Ω
- B.20 Ω✓
- C.10 Ω
- D.100 Ω
Why: Series resistances add: 10 + 10 = 20 Ω.
Q10. Two 10 Ω resistors in parallel give a total of:
- A.20 Ω
- B.5 Ω✓
- C.10 Ω
- D.0 Ω
Why: For two equal resistors, parallel total = half the value = 5 Ω.
Q11. In a series circuit, the current is:
- A.The same through every component✓
- B.Different in each component
- C.Zero
- D.Always alternating
Why: Series = one path = same current; the voltage divides.
Q12. The reactance of a capacitor as frequency increases:
- A.Decreases✓
- B.Increases
- C.Stays the same
- D.Becomes infinite
Why: ecreases. Capacitive reactance falls with frequency (a capacitor passes high frequencies more easily).
Q13. A tuned LC circuit is used in a radio to:
- A.Generate DC
- B.Select one frequency and reject others (tuning)✓
- C.Increase resistance
- D.Store charge only
Why: At resonance an LC circuit responds sharply to one frequency — the basis of tuning.
Q14. The speed of radio waves in free space is approximately:
- A.3 × 10&sup6; m/s
- B.3 × 10&sup8; m/s✓
- C.300 m/s
- D.1013 m/s
Why: Radio waves travel at the speed of light ≈ 3 × 10&sup8; m/s.
Q15. As frequency increases, wavelength:
- A.Decreases✓
- B.Increases
- C.Stays the same
- D.Doubles
Why: ecreases. Inversely proportional: c = f × λ with c fixed.
Q16. The wavelength of a 150 MHz signal is:
- A.0.5 m
- B.2 m✓
- C.20 m
- D.200 m
Why: λ = c/f = 3×10&sup8; ÷ 150×10&sup6; = 2 m.
Q17. The period of a 1 MHz signal is:
- A.1 second
- B.1 millisecond
- C.1 microsecond✓
- D.1 nanosecond
Why: T = 1/f = 1 ÷ 1,000,000 = 1 µs.