# 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.

### Limitations of Terzaghi Theory

Limitations of Terzaghi Theory The value of the coefficient of consolidation has been assumed to be constant.  The distance d of the drainage path cannot be measured accurately in the field. The thickness of the deposit is generally variable, and an average value has to be estimated.  There is sometimes difficulty 1n locating the drainage face, and sometimes thin previous seams that can act as good drainage faces are missed in the boring operations. The equation is based on the assumption that the consolidation is one-dimensional. In the field, the consolidation is generally 3-dimensional. The lateral drainage may have a significant effect on the time rate of consolidation. The initial consolidation and secondary consolidation have been neglected. Sometimes these form an important part of the total consolidation. In actual practice, the pressure distribution may be far from linear or uniform.

### Streamer Theory of Breakdown in Gases

Streamer Theory of Breakdown in Gases According to the Townsend theory firstly, current growth occurs as a result of the ionization process only. But in practice, breakdown voltages were found to depend on the gas pressure and the geometry of the gap. Second chances time lags of the order of 10-5 s, but practically it was observed to occur at a very short time of 10-8 s. Also, the Townsend mechanism predicts a very diffused form of discharge, that actually discharges were found to be filamentary and irregular. Townsend's mechanism failed to explain all these observed phenomena and as a result, The Streamer theory was proposed. The theory predicts the development of a spark discharge directly from a single avalanche in which the space charge developed by the avalanche itself is said to transform the avalanche into a plasma steamer. In Fig 1.7, a single electron starting at the cathode by ionization builds up an avalanche that crosses the gap. The electrons in the a

### Price Guard Wire Method

Price Guard Wire Method Some form of  Price Guard Wire Method  is generally used to eliminate the errors caused by leakage currents over insulation. Fig. 3.14 illustrates the operation of This Method. In fig 3.14(a), a high resistance mounted on a piece of insulating material is measured by the ammeter voltmeter method. The micro-ammeter measures the sum of the current through the resistor (IR) and the current through the leakage path around the resistor. The measured value of resistance computed from the readings indicated on the voltmeter and the microammeter, will not be a true value but will be in error.   Figure 3.14 Application of  guard  circuit for measurement of high resistance In fig, 3.14 (b), the  guard  terminal has been added to the resistance terminal block. The  guard  terminal surrounds the resistance terminal entirely and is connected to the battery side of the micro-ammeter. The leakage current IL now