# Electrical Measurements Questions and Answers – Sources and Detectors

This set of Electrical Measurements & Measuring Instruments Multiple Choice Questions & Answers (MCQs) focuses on “Sources and Detectors”.

1. At very low frequencies in a AC bridge, the source is _________
a) power line
b) e.m.f
c) galvanometer
d) tuned circuit

Explanation: Galvanometer is used for detecting the balance condition. The power line acts as a source of supply for bridge measurements in an AC bridge circuit at very low frequencies.

2. At high frequencies in an AC bridge, the source is _______
a) tuned amplifiers
b) oscillators
c) vibration galvanometer
d) high voltage source

Explanation: Tuned amplifiers are used as a source of voltage in AC bridges. Electronic oscillators are used as a source of supply for bridge measurements in an AC bridge circuit at high frequencies.

3. The frequency range of a typical oscillator is _______
a) 1 Hz to 50 Hz
b) 1 kHz to 100 KHz
c) 40 Hz to 125 kHz
d) 1 MHz to 150 MHz

Explanation: An oscillator has a frequency range slightly above the audio frequency. A typical oscillator has a frequency range of 40 Hz to 125 kHz.

4. The power output for a typical oscillator is _______
a) 1 kW
b) 1 MW
c) 1 mW
d) 7 W

Explanation: Oscillator usually has a low power output. A typical oscillator has a power output of around 7 W.

5. The output waveform in an oscillator is _______
a) sinusoidal
b) cosinusoidal
c) tangential
d) logarithmic

Explanation: AC supply is generally in the form of sinusoidal signal. In an electronic oscillator, output waveform is very close to sinusoidal.
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6. The output frequency of an oscillator is _______
a) unstable and fixed
c) stable and fixed
d) unstable and variable

Explanation: In an electronic oscillator, the output frequency is stable. It can be determined accurately and is also adjustable.

7. The output power of an oscillator is not enough to drive power circuits.
a) True
b) False

Explanation: Power circuits generally require a low output in order to function. An electronic oscillator provides sufficient output power to drive power circuits.

8. Tuned amplifiers can be set to _______
a) low frequencies
b) high frequencies
c) any frequency
d) audio frequencies

Explanation: Tuning refers to varying a parameter. Tuned amplifier circuits can be set to any desired frequency.

9. Tuned amplifier circuits respond to broad bandwidth at bridge frequency.
a) True
b) False

Explanation: Amplifiers can be used to detect the balance condition in AC bridges. Tuned amplifier circuits consist of transistors that respond to a narrow bandwidth at the bridge frequency.

Sanfoundry Global Education & Learning Series – Electrical Measurements.

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