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Objective Questions

Short notes

Objective questions (Answers are given below)

Digital instruments are those which
(a) have numerical readout
(b) use LED or LCD displays
(c) have a circuitry of digital design
(d) use deflectioin type meter movement.
The main difference between the electronic and
electrical instruments is that an electronic instrument
contains
(a) an electronic device (b) a transducer
(c) a digital readout (d) electrons.
The essential elements of an electronic instrument
are
(a) transducer (b) signal conditioner
(c) indicating device (d) all of the above.
The current sensitivity of a meter is expressed in
(a) ampere (b) ohm/ampere
(c) ohm/volt (d) ampere/division.
The basic meter movement can be converted
into an ohmmeter by connecting a …..with it.
(a) high resistance in series
(b) low resistance in parallel
(c) battery in series
(d) battery and a variable resistance in series
The D’ Arsonval meter movement can be converted
into an audio-frequency ac ammeter by
adding a …… to it.
(a) thermocouple (b) rectifier
(c) chopper (d) transducer.
In a linear meter, half-scale deflection occurs
when there is … per cent of the rated current
through its coil
(a) 100 (b) 25
(c) 50 (d) 75
A 0-1 mA meter has a sensitivity of
(a) 1 k Ω/V (b) 1 mA
(c) 1 k Ω (d) 1000 A.
A moving coil instrument has a resistance of 10 Ω
and takes 40 mA to produce full-scale deflection.
The shunt resistance required to convert this instrument
for use as an ammeter of range 0 to 2 A
is
(a) 0.1021 Ω (b) 0.2041 Ω
(c) 0.2561 Ω (d) 0.4210 Ω
A moving coil ammeter has a fixed shunt of 0.02
ohm resistance. If the coil resistance of the meter
is 1000 Ω, a potential difference of 500 mV is required
across it for full-scale deflection. Under
this condition, the current in the shunt would be
(a) 2.5 A (b) 25 A
(c) 0.25 A (d) 0.025 A
It is desired to convert a 0-1000 μA meter movement,
with an internal resistance of 100 Ω into
a 0-100 mA meter. The required value of shunt
resistance is about
(a) 1 Ω (b) 10 Ω
(c) 99 Ω (d) 100 Ω
Loading effect is principally caused by… instruments
(a) high resistance (b) low-sensitivity
(c) high-sensitivity (d) high-range
A multimeter is used to measure
(a) resistance (b) current
(c) voltage (d) all of the above
A sinusoidal voltage of rms value 10 V is applied
to a D’ Arsonval movement connected in series
with a half-wave rectifier. It will show a reading
of… volt
(a) 9 (b) 4.5
(c) 10 (d) 7.7
A VTVM produces negligible loading effect on
a circuit under test primarily because
(a) it virtually drawn no current from the circuit
(b) of its very high internal resistance
(c) it uses high vacuum tubes
(d) it is a null deflection instrument.
In a 3½ digit voltmeter, the largest number that
can be read is
(a) 0999 (b) 1999
(c) 4999 (d) 9999
A 3½ digit voltmeter having a resolution of 100
mV can be used to measure maximum voltage of
(a) 100 V (b) 200 V
(c) 1000 V (d) 5000 V
The signal to be observed on the screen of an
oscilloscope is applied
(a) across its X-plates (b) across its Y -plates
(c) to the horizontal amplifier
(d) to the trigger circuit.
When a 30 V dc is applied to the vertical deflection
plates of a cathode ray tube, the bright spot moves 1 cm away from the centre. If 30 V(rms) ac is applied, then the movement of the spot will be nearly

(a) 1 cm (b) 1.5 cm
(c) 2 cm (d) 3 cm

Production of a steady stationary display of a
signal waveform on the scope screen is due to
(a) persistence of vision
(b) flourescent material of the screen
(c) proper sync. between the signal and the
sweep generator
(d) electrostatic focussing of the electron beam.
Two sinusoidal signals of frequency f and 3f are
applied at x and y inputs respectively to an oscilloscope.
Which one of the following patterns
can be observed on the screen ?
(a) (b)
(c) (d)
The X- and Y -inputs of a CRO are respectively
V sin wt and −V sin wt. The resulting Lissajous
pattern will be
(a) a straight line (b) a circle
(c) an elipse (d) a figure of eight
The deflection sensitivity of a CRT depends inversely
on the
(a) length of the vertical deflecting plates
(b) distance between screen and deflecting plates
(c) deflecting voltage
(d) separation between Y -plates.
Two complete signal cycles would be displayed
on the screen of a scope when time-period of
the sweep generator is …… the signal time period.
(a) half (b) twice
(c) equal (d) thrice
A non-triggered oscilloscope is one which
(a) has no sweep generator
(b) cannot produce a stable stationary screen
display
(c) has a continuously running time-base genera
tor
(d) can display a portion of the input signal
wave form.
A dual-trace CRO has
(a) one electron gun (b) two electron guns
(c) one electron gun and one two-pole switch
(d) two electron guns and one two-pole switch
The operation a Q-meter is based on
(a) self-induction (b) series resonance
(c) mutual induction (d) eddy currents.
The resolution of a logic analyser is
(a) maximum number of input channels
(b) the minimum duration of the glitch it can
capture
(c) its internal clock period
(d) the minimum amplitude of the input signal
it can display
A spectrum analyser can be described as
(a) voltage selective frequency meter
(b) current selective frequency meter
(c) frequency selective voltmeter
(d) None of these

(c) 2. (a) 3. (d) 4. (c) 5. (d) 6. (b) 7. (c) 8. (a) 9. (b) 10. (b) 11.(a) 12. (b) 13. (d) 14. (b) 15. (b) 16. (a) 17. (c) 18. (a) 19. (a) 20. (c) 21.(b) 22. (a) 23. (d) 24. (b) 25. (c) 26. (c) 27. (b) 28. (a) 29. (d)

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