# Job interview Questions

Essential Electrical Engineering questions and answers center around all zones of Basic Electrical Engineering subject covering in Basic Electrical Engineering. These points have browsed an accumulation of the most legitimate and best reference books on Basic Electrical Engineering.

## 1. Why is RC coupling called so?

Ans. It is because in this arrangement the voltage developed across collector load (RC) in one stage is coupled through a capacitor (CC) to the next stage.

## 2. Why is RC coupling employed in the initial stages of a multistage amplifier?

Ans. The initial stages of a multistage amplifier are required to do the job of voltage amplification and this is aptly done by RC coupling due to the least frequency distortion. However, the final stage is expected to deliver maximum power to the output device e.g. speaker. For this purpose, impedance matching is the required-a quality which an RC coupled amplifier does not possess because of its output. impedance is several hundred ohms compared to a few ohms impedance of a speaker.

## 3. Why is transformer coupling not used in the initial stages of a multistage amplifier?

Ans. A transformer coupling has a high-frequency distortion. If it is employed in the initial stages, the output may have intolerable frequency distortion due to amplification by various stages.

## 4. Why is transformer coupling invariably employed in the final stage of a multistage amplifier?

Ans. Transformer coupling provides excellent impedance matching. Usually, the impedance of the output device (e.g. a speaker) is a few ohms whereas the output impedance of transistor 1‘ several hundred times this value. In order to match impedance, at step-down transform" of proper turns ratio is used. Impedance matching permits the transference of maximum power to the output device which is really the goal in the final stage.

## 5. Why does transformer coupling tend to introduce hum in the circuit?

Ans. There are hundreds of turns of primary and secondary in the transformer. These turns will multiply an induced e.m.f. from nearby power wiring. As the transformer is connected to the base circuit, therefore, the induced hum voltage will appear in amplified form in the output.