SSC JE electrical question paper explained 2016-2017

Explanation:

• Hysteresis motor develops hysteresis torque which is extremely steady both in amplitude and phase.

Explanation:

• Saturation is the state reached when an increase in applied external magnetic field H cannot increase the magnetization of the material further, so the total magnetic flux density B levels off.
• The air gap is mostly used in the magnetic circuit because magnetic saturation causes loss of inductance, increasing current, and power loss in the circuit.
• implementation of the air gap in a magnetic circuit extends the range before magnetic saturation occurs and increases the saturation current of the magnetic inductor.

Explanation:

The speed of the motor is given as

Ns =120f/P

=120 x 60/4

= 1800 rpm

Explanation:

The SI unit of magnetic flux is the weber (Wb) (in derived units: volt-seconds)

Explanation:

• In order to neutralize the cross magnetizing effect of armature reaction, a compensating winding is used.
• The compensating windings consist of a series of coils embedded in slots in the pole faces. These coils are connected in series with the armature. The series-connected compensating windings produce a magnetic field, which varies directly with the armature current.

Explanation:

In free space,

B=μ_oH

Where,

B is the magnetic flux density,

H is the magnetic field intensity

μ_o is the permeability of free space

Explanation:

• In series combination the equivalent resistance is added up R1 + R2 = 2R
• While in series combination the equivalent capacitance become 1/C1 + 1/C2 = C/2

Therefore for resistance the equivalent resistance increase and for capacitance equivalent capacitance decrease in the case of the series combination.

Explanation:

The spring gives controlling torque and is connected in series with the coil. If the spring is snapped, there will be no deflection. Hence the pointer will come in its initial position i.e zero

Explanation:

Specific Resistance

For any given material at a certain given temperature, the resistance is given as

where ρ is a constant depending on the nature of the material of the conductor and is known as its specific resistance or resistivity.

Specific Resistance depends only on the temperature and material of the conductor but not on its dimensions of the conductor, on which resistance depends, and mechanical deformation such as stretching, etc. As ρ depends only on the material of a conductor at a given temperature, hence it is a characteristic constant.