# What does the shunt resistance component in the equivalent circuit of an Induction motor represent ?

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What does the shunt resistance component in the equivalent circuit of an Induction motor represent ? (A) Windage and frictional loss only (B) Core losses only (C) Core, windage and frictional loss (D) Copper losses in rotor

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In the equivalent circuit of a 3-phase induction motor, the mechanical load on the motor can be represented by a resistance of value (1) R2 (2) R2/S (3) R2(1-S)/S (4) (R2/S)+1

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What is the equivalent resistance of a network having 5 resistors of each 10ohm connected in parallel?  (A) 10 Ohms (B) 50 Ohms (C) 500 Ohms (D) 2 Ohms

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A dc shunt motor runs at 500 r.p.m at 220 V. A resistance of 4.5 Ω is added in series with the armature for speed control. The armature resistance is 0.5 ohms. The current to stall the motor will be (1) 44 A (2) 50 A (3) 44.4 A (4) 60 A

In an induction motor high rotor resistance is required for (a) Power factor and low starting current (b) high power factor and high starting current (c) high power factor and low starting current (d) low slip and high efficiency

A synchronous motor has better power factor as compared to that of an equivalent induction motor. This is mainly because?

The slip of an induction motor normally does not depend on  (A) rotor speed (B) synchronous speed (C) shaft torque (D) core-loss component

Each branch of Y-connected load has resistance of 10 Ω. The resistance of each branch of an equivalent ∆-connected load will be   (a) 30 Ω (b) 100 Ω (c) 110 Ω (d) None of these

A shaded pole induction motor does not have the advantage of   (a) Rugged construction (b) Low initial as well as maintenance cost (c) High starting torque (d) Comparatively small starting current

A centre zero ammeters connected in the rotor circuit of a 6-pole 50 Hz induction motor makes 30 oscillations in one minute. The rotor speed is

Reduction in supply voltage by 10% will change the torque of an induction motor by   (a) 38% (b) 19% (c) 9.5% (d) No change

Why does the speed of a DC shunt motor decrease as the load increases?

What does the discharge transistor do in the 555 timer circuit?  (A) Discharge the external capacitor to stop the timing (B) Charge the external capacitor to stop the timing (C) Discharge the external capacitor to start the timing over again (D) Charge the external capacitor to start the timing over again

A moving coli ammeter has a fixed shunt of 0.02 Ω with a coil circuit resistance of R=1 kΩ and needs potential of 0.5 V across it for full scale deflection. Calculate the value of shunt to give full scale deflection when the total current is 10 A. (1) 0.05 Ω (2) 0.005 Ω (3) 0.5 Ω (4) 0.0005 Ω

A star circuit has element of resistance R/2. The equivalent delta elements will be?

Armature shunting method of speed control of dc shunt motor is preferred over annature resistance method due to:  (1) Better speed regulation (2) Less loss in external resistance (3) Simplicity in control circuit (4) Reduced cost of controller

In a dc shunt generator critical field circuit resistance line is the line drawn (A) above the OCC (B) below the OCC (C) tangent to the saturation curve (D) tangent to the linear portion of OCC

The meter which does not have any component in it to provide control torque is (A) Electrodynamometer for current measurement (B) Electrodynamometer for voltage measurement (C) Electrodynamometer for power measurement. (D) Electrodynamometer for power factor measurement.

During 3-phase short circuit on a unloaded alternator, the dc component may be zero in (1) One phase only (2) Any two phases (3) All three phases (4) None of the above

In a split-phase induction motor, the resistance/reactance ratios of windings are such that (A) current in the auxiliary winding leads the current in the main winding (B) current in the auxiliary winding lags the current in the main winding (C) both windings develop the same starting torque (D) both windings develop high starting current

A change of 5% in supply voltage to an induction motor will produce a change of approximately (a) 5% in the rotor torque (b) 7.5% in the rotor torque (c) 10% in the rotor torque (d) 25% in the rotor torque

When a dipole antenna of 1/8 length has an equivalent total resistance of 1.5 Watt then the efficiency of the antenna is   (A) 0.89159% (B) 8.9159% (C) 89.159% (D) 891.59%

A DC shunt motor having unsaturated magnetic circuit runs at 1000 rpm with rated voltage If the applied voltage is reduced to half of the rated voltage, the motor will run at (A) 2000 rpm (B) 1000 rpm (C) 750 rpm (D) 500 rpm

Why does induction motor have high starting current?

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What is the purpose of providing a fuse in an electric circuit?  (A) To safe guard the installation against heavy current (B) To reduce the current flowing in the circuit (C) To reduce the power consumption (D) To improve power factor

What is the direction of flow of electric current in an electric circuit?

The direction of rotation of an ordinary shaded pole single phase induction motor (1) Can be reversed by reversing the supply terminal connections to the stator winding (2) Cannot be reversed (3) Can be reversed by open circuit the shading rings (4) Can be reversed by short circuit the shading rings

For applications requiring speed ratio other than 2 : 1, the speed control of an induction motor can be effected by varying the number of stator poles employing  (1) multiple stator winding (2) pole amplitude modulation technique (3) consequent pole technique (4) Any of these

At low values of slip, the torque of an induction motor is   (a) directly proportional to the square of the slip. (b) inversely proportional to the square of the slip. (c) directly proportional to the slip. (d) inversely proportional to the slip.

The stator of an induction motor is made of  (a) carbon (b) wood (c) copper stampings (d) silicon steel laminators

The synchronous speed of an 8 pole induction motor supplied power from a 50 Hz source will be ?

The effect of increasing the length of air gap in an induction motor is to increase the (a) power factor (b) speed (c) magnetising current (d) air gap flux

The ratio of rotor output to rotor input in an induction motor is 0.96. The slip of the motor is (a) 0.04% (b) 4% (c) 6% (d) 12%

The frequency (fr) of the rotor current in an induction motor is given by the expression (s = slip, f = supply frequency)

A change of 4% in the supply voltage to an induction motor will produce a change of approximately

In an induction motor if the flux density is reduced to one-half, of its normal value then the torque will  (1) reduce to one-half (2) reduce to one-fourth (3) remain unchanged (4) increase four times