Increasing current means increasing frequency of the motor because current is directly proportional to rotations of the motor rotor

answered
Jun 1, 2019
by
prasadnani

Description : Why does increase in current mean a decrease in voltage?

**Answer** : This is because current flows from high potential to low potential to bring the two diffrent potential to unity , thus a reduced potential (voltage)

Description : How can we increase the induced current?

**Answer** : Induced current can be increased by reducing no of windings on the secondary part compared to primary.

**Answer** : The size of a synchronous motor decreases with the increase in flux density.

**Answer** : In a D.C. shunt motor, under the conditions of maximum power, the current in the armature will be more than full-load current.

Description : A 200 V dc shunt motor is running at 1000 rpm and drawing a current of 10 A. Its armature winding resistance is 2 Ohm. It. is braked by plugging. The resistance to be connected in series with armature to restrict armature current to 10 A, is

**Answer** : A 200 V dc shunt motor is running at 1000 rpm and drawing a current of 10 A. Its armature winding resistance is 2 Ohm. It. is braked by plugging. The resistance to be connected in series with armature to restrict armature current to 10 A, is 36 Ohm

Description : What are three ways you can increase the strength of an electromagnet?

**Answer** : In a synchronous motor, the armature current has large values for high and low excitation.

**Answer** : The armature current of the synchronous motor has large values for low and high excitation.

Description : Why does induction motor have high starting current?

**Answer** : In induction motor , the flux produce is quadrature to the applied voltage. Since when we are going to start motor , there is no flux present inside . So in order to lets say compensate it ... times of current to further increase flux. So that is reason for high starting current in induction motor

Description : What will happen if the induction motor runs at synchronous speed ?

**Answer** : Since there is always slip present in rotor it cannot run at synchronous speed no current will be developed hence no torque will developed

**Answer** : In a D.C. series motor, if the armature current is reduced by 50%, the torque of the motor will be equal to 25% of the previous value.

Description : Reduction in core losses and increase in permeability are obtained with transformer employing?

**Answer** : Reduction in core losses and increase in permeability are obtained with transformer employing core built-up of laminations of cold rolled grain oriented steel.

Description : For given applied voltage, with the increase in frequency of the applied voltage?

**Answer** : For given applied voltage, with the increase in frequency of the applied voltage eddy current loss will remain unchanged.

Description : what will happen when excitation of an unloaded salient pole synchronous motor suddenly gets disconnected?

**Answer** : When excitation of an unloaded salient pole synchronous motor suddenly gets disconnected the motor will stop.

Description : What would happen if a DC motor was supplied with AC ?

**Answer** : With three phase induction motor, humming and not rotate, but if single phase universal motor like air blower, home mixture, motor run on constant speed..speed variation not possible...

Description : 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

**Answer** : In an induction motor if the flux density is reduced.to one-half, of its normal value then the torque will reduce to one-fourth

**Answer** : If starting winding of a single-phase induction motor is left in the circuit, it will draw excessive current and overheat.

**Answer** : The current drawn by the armature of D.C. motor is directly proportional to the torque required.

**Answer** : The direction of rotation of universal motor can be reversed the by reversing the flow of current through either armature winding or field winding.

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

**Answer** : A change of 4% in the supply voltage to an induction motor will produce a change of approximately 8% in the rotor torque

**Answer** : In case the back e.m.f. and the speed of a D.C. motor are doubled, the torque developed by the motor will remain unchanged.

**Answer** : In case the conditions for maximum power for a D.C. motor are established, the efficiency of the motor will be less than 50%.

**Answer** : In case of a reluctance motor, when the load is increased so that it cannot maintain synchronous speed the motor will run as induction motor.

**Answer** : Flywheel is used with D.C. compound motor to reduce the peak demand by the motor, compound motor will have to be cumulatively compounded.

**Answer** : The mechanical power developed by a shunt motor will be maximum when the ratio of back e.m.f. to applied voltage is 0.5.

**Answer** : Cumulatively compounded D.C. motor will be suitable along with flywheel for intermittent light and heavy loads.

**Answer** : In a differentially compounded D.C. motor, if shunt field suddenly opens the motor will first stop and then run in opposite direction as series motor.

**Answer** : If the centrifugal switch does not open at 70 to 80 percent of synchronous speed of motor, it would result in damage to the starting winding.

Description : Torque developed by a three-phase, 400V, induction motor is 100 N -m. If the applied voltage is reduced to 200-V, the d'veloped torque will be

**Answer** : Torque developed by a three-phase, 400V, induction motor is 100 N -m. If the applied voltage is reduced to 200-V, the d'veloped torque will be 25 N -m

**Answer** : If a D.C. motor designed for 40°C ambient temperature is to be used for 50°C ambient temperature, then the motor is to be derated by a factor recommended by manufacturer and select the next higher H.P. motor.

**Answer** : For a D.C. shunt motor if the excitation is changed torque will change but power will remain constant.

**Answer** : If a D.C. shunt motor is working at no load and if shunt field circuit suddenly opens this will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses.

**Answer** : If a D.C. motor is to be selected for conveyors, Series motor would be preferred.

**Answer** : If the centrifugal switch of a two-value capacitor motor using two capacitors fails to open then Electrolytic capacitor will, in all probability, suffer break down.

Description : If the base current of a BJT is 250 µA and emitter current is 15 mA, then the common base current gain will be A) 0.98 B) 0.41 C) 59 D) 55

**Answer** : If the base current of a BJT is 250 µA and emitter current is 15 mA, then the common base current gain will be 0.98

Description : If the % reactance upto the fault point is 20%, then the short circuit current will be

**Answer** : If the % reactance upto the fault point is 20%, then the short circuit current will be 5 times the full load current

Description : If the fault current is 2000 A, the relay setting is 50% and CT ratio is 400:5, the plug setting multiplier will be

**Answer** : If the fault current is 2000 A, the relay setting is 50% and CT ratio is 400:5, the plug setting multiplier will be 10 A

Description : In a series R-C circuit, with the increase in frequency, current (A) Reduces (B) Increases (C) Does not change (D) Becomes zero

**Answer** : In a series R-C circuit, with the increase in frequency, current Increases

Description : The armature current on symmetrical 3 phase short circuit of a synchronous machine (salient pole) (A) has q -axis current only (B) has d -axis current only (C) has both d and q axis currents (D) cannot be divided between q and d axis currents

**Answer** : The armature current on symmetrical 3 phase short circuit of a synchronous machine (salient pole) has d -axis current only

Description : What will happen to the equilibrium price and quantity of peanut butter if peanuts increase in price and the price of jelly decreases? (a) the equilibrium price and quantity increase (b) the ... ) the equilibrium price will rise and the equilibrium quantity will be indeterminate (d) None of above

**Answer** : (c) the equilibrium price will rise and the equilibrium quantity will be indeterminate

Description : What will happen if a firm in perfect competitive market, increase its output by 50% (a)Total sales revenue will also increase by 50% ; (b) (b)Selling price will come down by 50%; (c)Total sales revenue will decrease by 50% ; (d)Profit will increase by 25%

**Answer** : (a)Total sales revenue will also increase by 50% ;

Description : If field current is decreased in shunt dc motor, the speed of the motor (a) remains same. (b) increases. (c) decreases. (d) none of the above.

**Answer** : increases

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