91. If a transformer has N1: N2 = 1:1, then the transformer is a/an ?
There are 3 types of transformers, as we know.
1-Step up transformer (N2>N1)
2-Step down transformer (N1>N2)
3-Isolation or one-to-one transformer (N2 = N1)
The question that you have asked refers to third type.
The transformers which are particularly designed to provide electrical isolation between primary and secondary circuits, without a change in voltage and current level are called isolation transformers.
As the name suggests, the use of transformers with unity turns ratio is to isolate two circuits operating at same voltage levels. (hence called isolation transformer)
When electrical equipment is used in a medical setting (or any other setting where electrical safety is a priority), an isolation transformer is considered as an essential (and legally required) part of the power supply chain.
92. Observe the figure and find the correct relation from the four given options ?
According to Kirchhoff’s law states that the current entering a node is always equal to the current leaving a node.
From the above Diagram
Current Flowing towards the Point: I1, I2, I6
Current Flowing Away from the Point: I3, I4, I5
Hence I1 + I2 + I6 = I3 + I4+ I5
93. During the....period the power supply to the motor is cut-off and the train is allowed to run due to its own momentum ?
94. Which of the following lamps is used s a sign or an indicator lamp ?
The lamp typically consists of a small glass capsule that contains a mixture of neon and other gases at a low pressure and two electrodes (an anode and a cathode).
A small version is used today mainly as indicator light in electronic instruments and appliances
95. The leakage coefficient in magnetic circuits is denoted by ?
λ
The ratio of the total flux produced to the useful flux set up in the air gap of the magnetic circuit is called a leakage coefficient or leakage factor. It is denoted by (λ).
96. Which of the following is the correct way of expressing the rating of a fuse ?
Fuses are rated in amperes because in a house, all the circuits run at the same voltage, but are wired with different size wire to support different workloads.
If you hook up a 20 amp load to a 10 amp circuit, you can heat up the wires enough to start a fire, without materially changing the voltage.
97. The function of compensation winding in AC series motor is to ?
If an ordinary d.c. series motor were connected to an a.c. supply the performance will not be satisfactory. Power factor will be low (because of high inductance of the field and armature circuits) and there will be an excessive eddy current loss in the yoke and field cores).
The eddy current loss can be reduced by laminating the core and yoke.
Power factor can be improved by reducing the reactance of field and armature windings. Field reactance is reduced by reducing the number of turns on the field winding. For a given current it will reduce the field m.m.f which will result in reduced air gap flux.
This will tend to increase the speed but reduce motor torque. To obtain the same torque, it will now be necessary to increase the number of armature turns proportionately.
This will however result in increased inductive reactance of the armature, so the overall reactance of the motor will not be significantly decreased.
Increased armature mmf can be neutralized effectively by using a compensating winding.
In conductively compensated motors the compensating winding is connected in series with the armature whereas in inductively compensated motors the compensating winding is short-circuited and has no interconnection with the motor circuit.
98. The maximum number of socket outlets allowed per power sub-circuit = ?
Indian Electricity Rules specify that the maximum load on a power sub-circuit should not exceed 3000 watts and the number of outlets should be limited to two..
99. Observe the given network and answer the question ?
For loop 1
Va = E1 − I1R1
Va = I3R3
For loop 2
Va = E2 − I2R2
100. ...voltage regulation is considered to be the best for transmission lines ?
Regulation of Transmission Line:
When the load is supplied, there is a voltage drop in the line due to resistance and inductance of the line and, therefore, receiving-end voltage VR is usually less than sending-end voltage VS.
The voltage drop i.e., difference of sending-end voltage and receiving- end voltage expressed as a percentage of receiving-end voltage is called the regulation.
VR% = (Vs-VR)/VR x100
It is always desirable that the voltage regulation of the line should be low, or in other words, the increase in the load current should lead to a small difference in the receiving-end voltage.
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