🧪 ECAT MCQ Quiz Hub

1. An alternating current or voltage
fluctuates off and on
varies in magnitude alone
changes its direction again and again
changes its magnitude harmonically and reverses its direction of flow after regularly recurring intervals.

2. A changing magnetic flux produces around itself an induced
Magnetic field
Electric field
Electromagnetic force
Artificial gravitational field

3. Electromagnetic waves travel in free space with the speed of
?-rays
Positive rays
Cathode rays
More than sound waves

4. The direction of propagation of an electromagnetic waves is
Perpendicular to electric field
Perpendicular to both electric and magnetic field
Perpendicular to magnetic field
Parallel to electric and magnetic field

5. An electromagnetic wave consists of
Electric and magnetic fields moving parallel to each other
Magnetic field moving with velocity of light in space
Electric field moving with velocity of light
Electric and magnetic fields moving perpendicular to each other

6. Electromagnetic waves transport
Energy
Momentum
Mass
Heat

7. Waves emitted from the antenna are
Sound waves
Electromagnetic waves
Radio waves
Modulated waves

8. Electromagnetic waves emitted from antenna are
Stationary
Longitudinal
Transverse
All the above

9. If capacitance of L-C circuit is made four times then frequency of the circuit becomes
Twice
One half
Four times
None

10. A capacitor of capacitance 30?F is charged by a constant current of 10mA. If initially the capacitor was uncharged what is the time taken for the potential difference across the capacitor to reach 300V?
0.9sec
15 sec
1.5x105sec
0.9x102sec

11. The value of the steady current which when flowing through the same resistor produces heat at the same rate as the mean rate of heat produced by the alternating current is
Average current
Sinusoidal current
r.m.s current
Net current

12. To find the r.m.s value of an alternating current mathematically we need to have
Mean value of I2
Square root of mean value of I2
Square root of I2
Square of 1/2

13. An alternating current of r.m.s value of 4.0 A and frequency 50Hz flows in a circuit containing 10? resistor. The peak current is then
20A
20.66A
6.66A
5.66A

14. An alternating current is represented by the equation I = I?sin?t which of the following equation represents an alternating current of frequency and amplitude twice that of the above current?
I = 2I?Sin(?t/2)
I = 2I?Sin(2?t)
I = 2ISin?t
I = I?sin(2?t)

15. pure resistor circuit the voltage and current are
Lagging each other
They are at 90? phase difference
They have zero phase difference
No phase difference

16. In capacitive circuit the current
Lags behind voltage by ?/2
Is in phase with voltage
Opposite in phase of voltage by ?
Leads forward the voltage by ?/2

17. A 100?F capacitor with 12V source in series having frequency 50Hz will offer a capacitive reactance of about
32?
62?
50?
100?

18. If a glass plate is inserted in between the plate of a capacitor in series with a lighted bulb the brightness of the bulb
Remains same
Brightness increases
Brightness decreases
No light

19. A pure variable resistor is connected in series with a pure capacitor of fixed capacitance. The impedance of the circuit
Remains
Becomes infinite
Becomes zero
Increases

20. A wire of resistance R is coiled inductively so that its inductance is L. The impedance of the coil at a frequency of f is
(R+2?fL)
(R2+?2L2)
(R2+f2L2)
(R2+4?2f2L2)

21. Ammeter connected in an AC circuit measures
Exact value of current
rms value of current
Net value of current
Peak value of current

22. When a pure inductor of inductance L and a pure capacitor of capacitance C are connected in parallel to a sinusoidal potential difference V the potential difference across both L & C will be
Same
Different
At L will be more than at C
At L will be less than at C

23. An alternating potential difference is connected across a pure resistor and the frequency of the supply is varied but the rms value of the voltage is kept constant. The mean rate of heat dissipated from the resistor is
Directly proportional to f
Directly proportional to ??f
Directly proportional to f2
Inversely proportional to f

24. What is the self inductance of a coil in which an induced emf of 2V is set up when the current changes at the rate of 4 As-1?
0.5 mH
0.5H
2.0H
8.0H

25. The frequency of a circuit consisting of a capacitance C and a resistor R is
C/R
R/C
1/RC
1/ ??RC

26. A 10? electric heater is connected to a 220V 50Hz mains supply. What is the peak value of the potential difference across the heater element?
220V
220/ ??2V
110V
220 ??2V

27. A choke is used as a resistance in
DC circuit
AC circuits
Both AC and DC circuit
Full wave rectifier circuit

28. At resonance the value of the power factor in an L-C-R series circuit is
Zero
half
1
not definite

29. An A.C series circuit containing 4? resistance and 3-? inductive reactance. The impedance of the circuit is
1?
5?
7?
7/?2?

30. An inductive coil has a resistance of 100?. When an AC signal of frequency 1000Hz is fed to the coil the applied voltage leads the current by 45?. What is the inductance of the coil?
10mH
12mH
16mH
20mH

31. Choose the correct statement. In the case of AC circuit ohms law holds for
Peak values of voltage and current
Effective values of voltage and current
Instantaneous values of voltage and current
All of the above

32. The phase angle between the voltage and the current in an AC circuit consisting of a resistance is
Zero
45?
90?
180?

33. In an LCR series circuit, if V is the effective value of the applied voltage VR is the voltage across R VL is the effective voltage across L & Vc is the effective voltage across C then
V = VR+VL+VC
V2 = VR2+VL2+VC2
V2 = VR2+(VL-VC)2
V2 = VL2+(VR-VC)2

34. a voltage V = V? cos ?t is applied across a resistor of resistance R the average power dissipated per cycle in the resistor is given by
V?/?2R
V?/?2?R
V?2/?2R
V?2/?2?R

35. Two identical coaxial circular loops carry equal currents in the same direction. If the loops approach each other the current in
Each increases
Each decreases
Each remains the same
One increases whereas that in the other decreases

36. An inductor may store energy in
its electric field
its coils
its magnetic field
both electric and magnetic fields

37. Tick the correct statement
the flight path of a vertically falling body appears straight to the stationary observer
the flight path of vertically falling body appears parabolic to an observer in uniform relative motion
all states of rest and motion are relative and there is no such thing as absolute motion
all the above

38. Mark the wrong statement.
a frame of reference which is either at rest or moves with a constant velocity is called an inertial frame of reference
an un-accelerated frame of reference is called an inertial frame of reference
all the frames of reference in uniform rectilinear motion are equivalent
Newtons laws of motion are valid in an accelerated (non inertial) frame of reference

39. The relativistic energy E is equivalent to relativistic mass given by
Ec2
E/c2
E/c
c2/E

40. An observer shoots parallel to a meter stick at very high (relativistic) speed and finds that the length of meter stick is
greater than one meter
less than one meter
one meter
a foolish question