A stand alone engine driven synchronous generator is feeding a partly inductive load. A capacitor is now connected across the load to completely nullify the inductive current. For this operation condition
A transistor may be used as a switching device or as a
In an ideal transformer primary and secondary induced emfs are
Factors affecting the values of resistances are
The function of starter in dc motor is to
Time delay relay is used
Murray loop test is used to locate the
Murray loop test is the most common and accurate method for locating earth faults and short-circuit faults.
The maximum efficiency for a transformer occurs at 80% of full load. Its core is Pc and ohmic loss is Poh at full load. For this, transformer, the ratio of Pc/Poh is
At low speed of three brush generator
The rotor of a stepper motor has no
A ceiling fan uses
The small pockets of air in the high voltage cable provide _____ relative permittivity,____ electric field and at these sites breakdown is likely to be initiated
Which of the following is correct ?
As compared to shunt and compound motors series motor have the highest torque becauseof its comparatively ____ at the start
Which element is used for making an electric iron element ?
A 2 cm long coil has 40 turns and carries a current of 650 mA. The magnetising force of the coil is
In a parallel a.c. circuit power loss is due to
An electric pyrometer is an instrument used to measure
A 200/100 V, 10 KVA transformer has 60 transformation ratio of the transformer ?
A synchronous capacitor is an over-excited motor running at
If 2% of the main current is to be passed through a galvanometer of resistance G, then resistance of the shunt required is
Star-delta starter of an induction motor
Correct Answer :- C
Explanation : The Star Delta Starter is a very common type of starter and is used extensively as compared to the other type of starting methods of the induction motor. A star delta is used for a cage motor designed to run normally on the delta connected stator winding.
Since the developed torque is proportional to the square of the voltage applied to an stator. Star delta starter reduces the starting torque to one-third that is obtained by direct delta starting.
In the circuit shown in the figure, i(t) is a unit step current. The steady-state value of v(t) is
Two coils have self inductances of 0.09 H and 0.01 H and mutual inductance of 0.015 H. The coefficient of coupling between the coils is
The configuration that can be used as a constant current source is
The DC current gain of a transistor in CE configuration is 100. Find its DC current gain in common base configuration
Starting torque of synchronous motor is
The maximum power developed in the synchronous motor will depend on
In an ac circuit Isinf is called
In the circuit shown in the figure below, the current supplied by the sinusoidal current source I is
Which of the following motors one will choose to drive the rotary compressor ?
The degree of mechanical vibrations produced by the laminations of a transformers depends on
A piece of oil soaked paper has been inserted between the plates of a parallel plate capacitor.Then the potential difference between the plates will
A coil with a certain number of turns has a specified time constants. If the number of turns is doubled, its time constant would
On doubling number of turns, inductance becomes four times as inductance is proportional to number of turns squared and resistance is only doubled, since time constant is inductance upon resistance, new time constant becomes 2T.
To maximize the driving torque in an induction type instrument, flux produced by shunt coil and series coil should be
If the supply polarity to the armature terminal of a separately excited d.c. motor is reversed, the motor will run under
Which of the following motor has high starting torque ?
Hysteresis loss in a dc machine are proportional to
In power station practice "spinning reserve" is
Grounding is generally done in transmission line at
For an electric arc welding the current range is usually
Current flow in a semiconductor depends on the phenomenon of
Maxwell inductance bridge is used for coil of Q value
Which one of the following is used for the measurement of 3-f power factor ?
The speed of the meter disc on full load is kept the lowest possible in order to
The current and potential coil of a wattmeter were accidentally interchanged while connecting.After energizing the circuit, it was observed that the wattmeter did not show the reading. This could be due to
Which voltmeter would you select for measuring 50000 V direct current ?
The secondary of CT is never left open circuited because otherwise
Rated breaking capacity (MVA) of a circuit breaker is equal to
While using air blast circuit breaker, current chopping is a phenomenon often observed when
The arc voltage in a circuit breaker is
The transformer efficiency at relatively light loads is quite low. This is due to