All Free Electrical Engineering MCQs with Answers

• A. Is increased
• B. Remains the same
• C. Is decreased
• D. None of the above

Explanation: The carrier amplitude and power are set by the unmodulated carrier and do not change with modulation depth.

• A. Fidelity
• B. Frequency range
• C. Sensitivity
• D. Selectivity

Explanation: A high-Q tuned circuit has a narrow bandwidth and strongly rejects frequencies away from resonance.

• A. Amplitude
• B. Frequency
• C. Phase
• D. Both phase and frequency

Explanation: Man-made noise is mainly produced by switching and sparking sources, which appear as random amplitude disturbances or electrical impulses.

• A. Carrier
• B. Sideband
• C. Carrier as well as sideband
• D. None of the above

Explanation: For AM, carrier power stays fixed, while sideband power is proportional to the square of the modulation index.

• A. Receiving antenna
• B. Transmitter
• C. Radio receiver
• D. Transmitting antenna

Explanation: Demodulation extracts the original information signal from the modulated carrier, and this process is performed in the radio receiver.

• A. Space
• B. An antenna
• C. Cable
• D. None of the above

Explanation: In radio transmission, electromagnetic waves travel through free space between the transmitting and receiving antennas.

• A. Frequency
• B. Phase
• C. Amplitude
• D. None of the above

Explanation: In standard television transmission, the picture information is carried by amplitude modulation, while the sound is generally frequency…

• A. IF stage
• B. Receiving antenna
• C. Audio stage
• D. RF stage

Explanation: Receiver noise is generally most significant in the RF and mixer portions at the front end, where weak received signals are first…

• A. mV
• B. µV
• C. V
• D. None of the above

Explanation: A radio receiver must detect very weak electromagnetic signals, so the voltage induced in its aerial is typically in the microvolt range.

• A. Hartley
• B. RC phase-shift
• C. Wien-bridge
• D. Crystal

Explanation: A crystal oscillator is preferred in a transmitter because its piezoelectric crystal provides highly stable and accurate frequency…

• A. Carrier
• B. Sidebands
• C. Both sidebands and carrier
• D. None of the above

Explanation: The carrier mainly conveys the signal to the sidebands and contains no original information in ordinary AM.

• A. Lower sideband
• B. Upper sideband
• C. Carrier
• D. None of the above

Explanation: In standard AM at or below 100% modulation, the carrier power is greater than the combined sideband power; at 100% modulation, the…

• A. Equal to
• B. Greater than
• C. Less than
• D. None of the above

Explanation: The modulation index is the ratio of signal amplitude to carrier amplitude, so 100% modulation means a modulation index of one.

• A. Amplitude
• B. Frequency
• C. Phase
• D. None of the above

Explanation: Amplitude modulation varies the carrier's amplitude in proportion to the instantaneous strength of the information signal.

• A. Transmitter
• B. Radio receiver
• C. Between transmitter and radio receiver
• D. None of the above

Explanation: Modulation combines the information signal with a high-frequency carrier before radiation, so it is performed in the transmitter.

• A. Thrice
• B. Four times
• C. Twice
• D. None of the above

Explanation: For a highest modulating frequency of f_m, an AM signal has sidebands at f_c minus f_m and f_c plus f_m.

• A. 50%
• B. 40%
• C. 60%
• D. 25%

Explanation: The power in each AM sideband is m²P_c/4, where m is the modulation index.

• A. Equal to
• B. Greater than
• C. Less than
• D. None of the above

Explanation: Amplitude overmodulation occurs when the modulation index exceeds 1, meaning the signal amplitude is greater than the carrier amplitude.

• A. Weakening of the signal
• B. Excessive carrier power
• C. Distortion
• D. None of the above

Explanation: When modulation exceeds 100%, the AM envelope crosses or becomes distorted, producing distortion in the transmitted signal.

• A. ac collector voltage is 180° out of phase with ac base voltage
• B. ac emitter voltage is 180° out of phase with ac base voltage
• C. ac collector voltage is in phase with ac base voltage
• D. none of the above

Explanation: In a common-emitter, or base-driven, amplifier, an increase in base voltage increases collector current and the voltage drop across the…