EE MCQ

SSC JE Electrical 2019 with solution SET-2
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The wattage rating of a single-phase induction motor used as a ceiling fan will be in the range of

The wattage rating for a ceiling fan motor is in the range of 50 to 150 W. if the ceiling Fans size ranges from 36 inches to 56 inches then the total wattage use is 55 to 100 watts.. A 48-inch ceiling fan will use 75 watts.

Related Question

SSC JE Electrical 2019 with solution SET-2
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The number of valence electrons of P and Si are respectively?

Phosphorus (P) has 15 electron i.e 2,8,5. Hence the number of electron in its outermost orbit is 5.

Silicon (Si) has 14 electron i.e 2,8,4. Hence the number of electrons in its outermost orbit is 4.

SSC JE Electrical 2019 with solution SET-2
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If a circular conductor carries a current of ‘I’ ampere having radius ‘r’ meter, then the magnetizing force at the center of the coil is given by

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

The magnetic Field strength at the center of circular loop carrying current I is given by

B = μoI/2r

B/μo = I/2r

H = I/2r At/m

Where r = Radius

SSC JE Electrical 2019 with solution SET-2
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In the salient pole of the phase synchronous machine, the rotor will have

The rotor of the synchronous machine carries a field winding that is supplied with d.c. through two slip rings by a separate d.c. source. Synchronous Rotor construction is of two types, namely :

Salient (or projections) pole type.

Cylindrical type (or non-salient pole type)**Salient-pole rotor:**-

In this type, salient poles are mounted on a large circular steel frame which is fixed to the shaft of the alternator.

The rotors of salient-pole rotor machines have concentrated winding on the poles and a nonuniform air gap.

Salient pole generators have a large number of poles. sometimes as many as 50, and operate at lower speeds.

The synchronous generators in hydroelectric power stations are of the salient pole type and are driven by water turbines.

The rotors are shorter axial length but have a large diameter.

SSC JE Electrical 2019 with solution SET-2
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The flux while crossing air gap tends to bulge outwards, thereby increasing the effective area of the gap, this effect is known as

Magnetic Fringing

When flux enters into the air gap, it passes through the air gap in terms of parallel ﬂux lines. There exists a force of repulsion between the magnetic lines of force which are parallel and having the same direction. Due to this repulsive force, there is the tendency of the magnetic flux to (spread out) at the edge of the air gap. This tendency of ﬂux to spread out at the edges of the air gap is called magnetic fringing.

Magnetic fringing increases the effective cross-sectional area of the air gap reduces the flux density. So leakage, fringing, and reluctance should be as small as possible. This is possible by choosing a good magnetic material and making the air Magnetic fringing gap as narrow as possible.

SSC JE Electrical 2019 with solution SET-2
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If a zero-centered voltmeter has a scale from 5V to − 5V, then the span of it is

Voltage Scale Span of instrument = Vmax − Vmin

Given

Vmax = 5 V

Vmin = −5V

Span = 5 −(−5) = 10 V