EE MCQ

SSC JE Electrical 2019 with solution SET-2
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IL = Load Current, then the relation between these currents for a DC series generator is

When the field winding is connected in series with the armature winding while supplying the load then the generator is called a series generator.

Current Relations

As all armature, field, and load are in series they carry the same current.

IL = Ise = Ia

Related Question

SSC JE Electrical 2019 with solution SET-2
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Four relations have been given. Select the correct relation?

The amount of flux produced by the magnet indicates the strength of the magnet. The more the magnetizing force (MMF), the more is the flux produced. The more the opposition to the flux path (i.e., reluctance or magnetic resistance) less is the flux produced. This relationship is expressed as

Flux = MMF/ Reluctance

Reluctance is the opposition offered by the material in the flux path to the establishment of the flux. The reluctance in a magnetic circuit is similar to the resistance in an electric circuit. Reluctance is the inverse of permeance.

MMF = Flux/Permeance

SSC JE Electrical 2019 with solution SET-2
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If the connected light load in a house is 3000W and power sub-circuit load 6000W, then what is the total number of sub-circuits required?

Indian Electricity Rules specify that the maximum load on a light/fan sub-circuit should not exceed 800 watts and the number of points should be limited to 10.

Hence for light load number of sub-circuit = 3000/800 = 3.75 = 4

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.

For the power sub-circuit load number of sub-circuit = 6000/3000 = 2

Total subcircuit = 4 + 2 = 6

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.