57. In a linear, an input of 5 sin cot produces an output of 10 cos wt. The output corresponding to input 10 cos wt will be used to
A. +5 sin on
B. ?5 sin on
C. +20 sin on
D. ?20 sin 03 t

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58.  When an ac voltage is applied to a PMMC voltmeter
A. the mater gets damaged
B. meter reading is zero
C. pointer will oscillate to and fro
D. the pointer will not move at all

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59.  A simple moving coil meter can not be used to measure radio frequency currents because
A. the meter would introduce an inductive reactance in the circuit
B. large heat dissipation results
C. damping of the meter becomes difficult of radio frequencies
D. the meter is not very accurate at radio frequencies

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60.  The error which does not result in moving iron instrument for both ac and dc measurements
A. stray magnetic field error
B. hysteresis error
C. eddy current error
D. temperature error

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61.  The advantage of a moving iron instrument is that
A. it has linear scale
B. its current sensitivity is high
C. it can be used under severe overload condition
D. it can be used at high frequencies

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62.  Moving iron meters can be used upto frequency of
A. 50 Hz
B. 100 Hz
C. 500 Hz
D. 1500 Hz

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63.  The advantage of electrodynamometer type of instruments is
A. low torque/weight ratio
B. large operating current
C. non uniform scale
D. the coil being air cored, these instruments are free from hysteresis and eddy current errors

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