Electrical Questions And Answers FreeElectrical interview questions for electrical alumni. Much of the time asked interview inquiries with answers under the subjects like electrical machines, Transmission and distribution, Power hardware and some broad essential questions.
Why do not we employ RC or transformer coupling for extremely low frequencies (< 10 Hz)
Ans. It is because, at such low frequencies (<10 Hz), the electrical and physical sizes of capacitors and transformers become too large.
Why should coupling capacitors in transistor amplifiers possess high values
Ans. A transistor amplifier (CE arrangement) has a low input impedance of the order of 500 Q or so. It is desired that reactance offered by the coupling capacitor should not be more than 20 9. To achieve this, large values of coupling capacitances must be used. Generally, the capacitance of coupling capacitors ranges from 1 ”F to 10 “F.
In a two-stage RC coupled amplifier; why are the capacitors required for the second stage smaller than those for the first stage
Ans. It is because the source resistance feeding the second stage is larger than that feeding the first.
What factor determines the low-frequency response of the RC or transformer-coupled amplifier
Ans. The low-frequency response is determined by the coupling device. In the low-frequency range, as the frequency decreases, the voltage gain also decreases. This is logical since the coupling elements (CC or transformer) are designed to block d.c.; hence the closer the signal frequency approaches direct current, the more the gain will be decreased by the coupling element.
What factor determines the high-frequency response of the RC or transformer-coupled amplifier
Ans. The high-frequency response is determined by the transistor itself. The transistor exhibits low inter-electrode capacitances which tend to decrease the gain.
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