183. Why are R?C oscillators unsuitable for radio-frequency applications?
A. At higher radio frequencies capacitors required have nonpractical values
B. Resistor and capacitors get heated up at higher frequencies
C. Resistors cause tremendous power loss at higher frequencies
D. none of these

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184. One of the following oscillator types in used for extremely stable output frequency
A. Resonant circuit oscillators
B. Resistance?capacitance oscillators
C. Weinbridge oscillators
D. Crystal oscillators

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185. One of the following electronic systems is an example of D.C. to A.C. conversion
A. Electronic rectifier
B. Electronic converter
C. Oscillators
D.Amplifiers

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186. In a practical clamping circuit, a resistor R is placed across the diode. This is
A. to provide charging or discharging path for the capacitor as the need arises
B. to neutralize the effect of diode's forward resistance
C. an indispensableaddition
D. none of these

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187. If the polarity of the diode in the above circuit is reversed, the circuit would behave
A. as a clipper
B. as a two level clipper
C. as a clamper
D. none of these

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188. If the step-up ratio of a pulse transformer is increased by a factor of 4, the rise time
A. increases by a factor of 2
B. increases by a factor of 16
C. decreases by a factor of 4
D. increases by a factor of 4

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189. In order to reduce the drop in the flat top portion of the pulse and the backswing at the end of the pulse, it is required to have
A. a very large value of magnetizing inductance
B. a very small value of leakage inductance
C. a very small value of stray capacitance
D. the step up ratio as small as possible .

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