EE MCQ

SSC JE Electrical 2019 with solution SET-1
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The trade name of the Nickel-Copper alloy, that is used as a heating element is:

Constantin‘, also known as ‘Eureka wire‘, is the trade-name for a copper-nickel alloy (approx. 60:40 ratio) formulated in the late 1800s by Edward Weston.

Related Question

SSC JE Electrical 2019 with solution SET-1
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4F2D is a/an number

The hexadecimal number system is also called base-16, a numeration system in which all numbers are represented using the symbols 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, and F only. The system is base of 16. The hexadecimal numbers are used to represent binary numbers because of ease of conversion and compactness.

SSC JE Electrical 2019 with solution SET-1
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A three-phase induction machine, when it is operating like a motor, the range of slip is given by

Torque speed characteristic of induction motor

Motoring mode: 0 ≤ s ≤ 1

For this range of slip, the load resistance in the circuit is positive, i.e. torque developed is in the direction in which the rotor rotates.

In this region the value of slip lies between 0 to 11 i.e., slip is positive.

The motor rotates in the same direction as that of a rotating magnetic field.

At s = 0 (synchronous speed), the torque produced by the motor is zero because the induced voltage in the rotor is zero when N= Ns.

The torque increases as the slip increases while the air gap flux remains constant.

The torque-slip characteristic from no-load to somewhat beyond full-load is almost linear.

Generating mode: s <0

In this operating mode, the slip s is negative i.e., s < 0. The slip will be negative if and only if the rotor speed N is greater than the synchronous speed Ns (N> Ns). However, the rotor and R.M.F both rotate in the same direction.

In this region, the motor acts as a generator and return the power back to a.c. source.

Braking or plugging Mode: s > 1

In this region, the value of slip is greater than 1 and the rotor rotates in the opposite direction of the rotating magnetic field.

This is achieved by interchanging any two phases of the stator supply.

SSC JE Electrical 2019 with solution SET-1
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An electric motor in which both the rotor and stator fields rotate with the same speed is called

In the synchronous motor, the stator and rotor rotate at the same speed.

SSC JE Electrical 2019 with solution SET-1
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In the circuit shown, if R = 0, then the phase angle between v(t) and i(t) is

In the given circuit if R = 0 then the circuit becomes purely inductive. So the phase angle between v(t) and i(t) is 90°.

SSC JE Electrical 2019 with solution SET-1
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The amount of AC content present in the DC output of a rectifier is given by

Ripple factor: The output of the rectifier is of pulsating d.c. type. The amount of a.c. content in the output can be mathematically expressed by a factor called the ripple factor (γ). The ripple factor expresses how much successful the circuit is, in obtaining pure d.c from a.c. input.

Less is the ripple factor, better is the performance of the circuit.

Ripple Factor γ = R.M.S value of a.c component of output ⁄ Average or d.c component of the output