EE MCQ

SSC JE Electrical 2019 with solution SET-1
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Which of the following is the correct relation regarding coupled coils?

Mutual inductance between two coupled coils is given by the relation

M = K√L1L2

Where

L1L2 = Inductance of the coil

K = Coefficient of coupling

When K = 1 coils are said to be tightly coupled and if K is a fraction the coils are said to be loosely coupled.

Here

Kmax =1

Kmin =0

∴ m ≤ (L1 L2 )0.5

Related Question

SSC JE Electrical 2019 with solution SET-1
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The law that explains about the economic size of a conductor is:

In transmission lines, a large amount of power is transmitted over a long distance. So, voltage regulation is not important because in some lines, 40% regulation is considered satisfactory. In such cases, only the economy is important. The cost of the conductor is the main part which decides the total cost of the transmission line. Hence, the selection of the proper size of the conductor for a particular line is most important.

The most economical area of the conductor is that for which the total annual cost of the transmission line is minimum. This is known as Kelvin’s law and was given by Lord Kelvin in the year 1881.

It states that the most economical cross-section of a conductor is the value at which the annual cost of the electric energy wasted in the conductor, and annual cost of the interest and depreciation on the capital cost of the conductor are equal. Thus, the total annual charge on an overhead transmission line can be expressed as :

Total annual charge =P1 + P2α or Variable part of the energy charge = Annual cost of energy wasted.

where

P1 and P2 are constants

α is the area of the X-section of the conductor.

SSC JE Electrical 2019 with solution SET-1
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Please check out below figure.

From the figure it can be concluded that the voltmeter reads 5 volts as shown in the figure below. Based on the voltmeter and ammeter readings in the measuring network, determine the value of the resistor R Here Current I = 1/2 A = 0.5 A Voltage V = 5 V R = V/I = 0.5/5 R = 10Ω

SSC JE Electrical 2019 with solution SET-1
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Z1 and Z2 are connected in series to form a load. A wattmeter’s current coil is connected in series with the load, whereas its pressure coil is connected across Z2. The wattmeter reads

As you can see from the below figure in load Z1 is connected with the only current coil. In Load Z2 both current from the current coil (CC) and voltage from voltage coil (PC) are present (Power = V × I). Hence the Wattmeter will read power consumed by Z2.

SSC JE Electrical 2019 with solution SET-1
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_______is a tube that brings water to turbines

Penstock

Penstock pipe is used to bring water from the dam to the hydraulic turbine.

Penstock pipes are made up of steel or reinforced concrete.

The turbine is installed at a lower level from the dam.

The penstock is provided with a gate valve at the inlet to completely close the water supply.

It has a control valve to control the water flow rate into the turbine.

SSC JE Electrical 2019 with solution SET-1
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In electric traction, the coefficient of adhesion is represented by

When two solid surfaces are brought into contact, a finite normal force is needed to pull the two solids apart. This force is known as the force of adhesion or simply adhesion.

The coefficient of adhesion () defined as the ratio of tractive effort required to propel the wheel of a locomotive to its adhesive weight. Adhesion traction is the friction between the drive wheels and the steel rail.

µ = Ft/W

Where

Ft = Tractive effort

W = Adhesive Weight