# Electrical Measurements Questions and Answers – Basic Principle of Signal Display

This set of Basic Electrical Measurements Questions and Answers focuses on “Basic Principle of Signal Display”.

1. What provides a periodic voltage waveform?
a) sweep generator
b) voltmeter
c) oscillator
d) amplifier

Explanation: Sweep generator provides a periodic voltage waveform in an oscilloscope. As the waveform resembles the teeth of a hacksaw it is known as a sawtooth waveform.

2. Visible spot must be moved in _______
a) two directions
b) one direction
c) three directions
d) four directions

Explanation: Sweep voltage must be brought to zero once it reaches its maximum value. The visible spot must be moved in a single direction only. Return sweep will trace back the signal in a reverse direction.

3. Spot is displayed only when _______
a) frequencies are different
b) frequencies are zero
c) frequencies are same
d) voltage is high

Explanation: When the sweep frequency and the signal frequency are same or integral multiple of each other, visible spot is displayed on the screen of the cathode ray oscilloscope.

4. What is done to make the trace horizontal?
a) negative voltage is applied
b) positive voltage is applied
c) no voltage is applied
d) voltage is synchronised

Explanation: The trace is made stationary by synchronising the sawtooth voltage with the magnitude of the signal that is applied to the vertical input.

5. A single cycle appears on the screen when _______
a) sweep and signal frequencies are equal
b) sweep and signal frequencies are not equal
c) sweep and signal frequencies are zero
d) sweep frequency is greater than signal frequency

Explanation: Many cycles are present on the screen when the sweep frequency is lower than the signal frequency. Only a single cycle appears on the screen when the sweep and signal frequencies are equal.

6. Sinusoidal voltage is not observed on the screen.
a) True
b) False

Explanation: Application of a sinusoidal voltage to the y terminal and the internally produced sawtooth voltage to the x terminal results in the shifting of the sawtooth voltage in terms of magnitude. Finally a sinusoidal waveform is observed on the screen.

7. What is the flyback period?
a) voltage is very high
b) current is very low
c) voltage is zero
d) current is very high

Explanation: During the flyback period, voltage suddenly drops to zero from a certain value.

8. During trace time, voltage is decreasing with time.
a) True
b) False

Explanation: The electron beam moves linearly along the horizontal direction during the trace time. The voltage Vx increases linearly with respect to time Tr during the instant of the trace period.

9. Light produced in a screen is _______
a) disappears immediately
b) does not disappear at all
c) is not visible to the eye
d) disappears slowly

Explanation: When the magnitude of the applied voltage reduces to zero, the light produced on the screen due to the bombardment of electrons does not disappear immediately and reduces in terms of intensity slowly.

Sanfoundry Global Education & Learning Series – Electrical Measurements.

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