Find real questions from previous competitive exam papers with answers and solutions.
Leave the keyword blank to browse saved questions for your selected exam, newest papers first. Add a keyword, year or topic to narrow the results.
Browse complete papersThe main purpose of a clamper circuit is to:
Introduce a DC level into the AC signal.
Suppress variations in signal voltage
Raise +ve half cycle of the signal.
Lower -ve half cycle of the signal.
Correct answer
Introduce a DC level into the AC signal.
Without a DC source, a clipper circuit acts like a:
Clamper
Chopper
Rectifier
Demodulator
Correct answer
Clamper
A single-phase diode bridge rectifier supplies a highly inductive load (ripple-free current). The AC supply-side current waveform is:
Sinusoidal
Constant dc
Square
Triangular
Correct answer
Sinusoidal
What is the SI unit for luminous flux?
Candela
Lumen
Lumens/m2
Lux
Correct answer
Candela
For an isotropic light source of luminous intensity 1 candela, what is the total luminous flux emitted in all directions?
\(\pi\) lumens
\(2\pi\) lumens
\(3\pi\) lumens
\(4\pi\) lumens
Correct answer
\(\pi\) lumens
A three-phase induction motor has maximum torque to full-load torque ratio of 2.5 : 1, with rotor resistance 0.5\(\Omega/phase\) and reactance 4\(\Omega/phase\). Find the star-delta starting torque to full-load torque ratio.
1.503
0.205
5.73
9.83
Correct answer
1.503
A 220V shunt motor has armature resistance 0.4\(\Omega\), takes 20A on full load at 750rpm. With an additional 0.6\(\Omega\) in the armature circuit, find the stalling torque to full-load torque ratio.
12.2
13
21
11
Correct answer
12.2
The rotor of an 8 - pole, 50Hz, 3 - phase induction motor has a rotor resistance of 0.4\(\Omega/phase\) and runs at a speed of 720rpm. For a constant load torque, calculate the additional rotor resistance/phase that must be inserted to reduce the speed by 25%.
1.8
2.1
2.4
4.8
Correct answer
1.8
A cascade set of two induction motors (A : 6poles, B : 8poles) is supplied from a 60Hz 3 - phase supply. Calculate the synchronous speed of the cumulative cascade set.
514.3 rpm
554 rpm
578 rpm
600 rpm
Correct answer
514.3 rpm
Which of the following is the most important reason for the preference of AC motors over DC motors in modern electric drives?
AC motors produce higher starting torque
AC motors do not require speed control
AC power can be transmitted easily with low line losses
AC motors are only used for constant speed applications
Correct answer
AC motors produce higher starting torque