Skip to main content

Electrical Questions And Answers Free

Electrical Questions And Answers Free

Electrical 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.

Electrical Questions And Answers Free

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.

Popular posts from this blog

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, sometimes thin previous seams that can act as good drainage face 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. Read More Muller-Breslau principle

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

Negative Booster

Negative booster A negative booster is employed to conform to the regulation that the potential difference between any two points of the rail return shall not exceed 7 V. Two boosters, positive and negative, are used which are mechanically coupled together and driven by a DC motor. The positive booster is connected to the trolley wire (near the generating station) and the negative booster (separately excited) is connected to the track rail.  The 'positive booster' adds voltage to the line while the 'negative booster lowers the potential of the point it is connected to. As we go along the trolley wire away from the generating station/sub-station, the potential drop increases, and the voltage of the trolley wire falls. Since the current returns via the track rail points away from the generating station acquire high potentials. This potential is brought down by the negative boost provided by the negative booster. When the load is sufficiently far aw