EE MCQ

SSC JE Electrical 2019 with solution SET-1
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An alternator has 9 slots/pole. What is the value of the pitch factor if each coil spans 8 slot pitches

Coil Span = 8

Pole Pitch = 9 slots/pole

Slot angle (α) = 180° / Pole Pitch = 180°/9 = 20°

Pitch Factor = cos(α/2) = cos (20/2)

Pitch Factor = cos 10°

Related Question

SSC JE Electrical 2019 with solution SET-1
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Three lamps are connected in series across a 120V supply and take a current of 1.5A. If the resistance of two of the lamps is 30Ω, what is the resistance of the third lamp?

Method 1

Supply Voltage = 120 V

Current I = 1.5 A

Total Resistance R = V/I = 120/1.5 = 80 Ω

Now resistance of 3 lamp be R1, R2, & R3

Req = R1 + R2 + R3

80 = 30 + 30 + R3

R3 = 20 Ω

Method 2

Applying KVL on the above circuit

120 = 1.5(R1 + R2) + 1.5R3

120 = 1.5(30 + 30) + 1.5R3

120 = 90 + 1.5R3

R3 = 30/1.5

R3 = 20 Ω

SSC JE Electrical 2019 with solution SET-1
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Hysteresis loss is NOT a function of

Hysteresis Loss = Kh × BM1.67 × f × v watts

where

Kh = Hysteresis constant depends upon the material

Bm = Maximum flux density

f = frequency

v = Volume of the core

Hence the hysteresis loss does not depend upon the ambient temperature.

SSC JE Electrical 2019 with solution SET-1
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The average value of a sinusoidal wave is:

The average value of the sine wave over one complete cycle is actually zero. Hence, for a sine wave, the average value is defined over half the period. The average value expressed in terms of peak value is given by

Average value = 0.637 × peak value

SSC JE Electrical 2019 with solution SET-1
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H = ____is the expression for the magnetic field due to an infinite linear current-carrying conductor

Magnetic Field Strength (H) gives the quantitative measure of strongness or weakness of the magnetic field.

H = B/μo

Where

B = Magnetic Flux Density

μo = Vacuum Permeability

Magnetic field due to infinite Linear current-carrying conductor is

B = μoI/2πr

B/μo = I/2πr

H = (I/2πr)A/m