Image
1.0.0
MCQ
21. The d.c. series motor should never be switched on at no load because-
the field current is zero
the machine does not pickup
the speed becomes dangerously high
it will take too long to accelerate
ব্যাখ্যা: No mechanical load on the series motor, the current is low, the counter-EMF produced by field winding is weak and so the armature most turn faster to produce sufficient counter EMF to balance the supply voltage. The motor can be damage by overspeed.
22. In an AC circuit, a low value of KVAR compared with kW indicates-
Low efficiency
High-power factor
Unity power factor
Maximum load current
23. In a highly capacitive circuit, the-
Apparent power is equal to the actual power
Reactive power is more than the apparent power
Reactive power is more than the actual power
Actual power is more than its reactive power
24. In the maximum value of a current of a circuit is 1 amp (sinusoidal wave). What is the R.M.S. value?
1 Amp
0.637 Amp
0.707 Amp
1.5 Amp
25. What will be the phase angle between two alternating waves of equal frequency, when one wave attains maximum value and the other is at zero value?
45°
90°
180°
30°
26. An air-core choke coil and an electric bulb are connected in series with ac mains. On introducing soft iron bar in the coil, the intensity of light will-
fluctuate
remain unchanged
increase
decrease
27. The capacitance of a capacitor is influented by-
Plate thickness
Plate separation
Plate area
Both (b) and (c)
28. The power of an AC circuit is given by-
VI cosθ
FZ
VI sinθ
FXL
29. How long does it take 50 µC of charge to pass a point in a circuit if the current flow is 15 mA?
3.33 x 10^3s
6 x 10^3s
6.33 × 10^3s
2s
30. The power factor of an ordinary electric bulb is--
Zero
Unity
Slightly more than zero
Slightly less than unity
ব্যাখ্যা: Basically ordinary electric bulb are resistive load. As resistive load they have unity power factor.
31. For an R-L load ---
Active power is greater than apparent power
Reactive power is greater than apparent power
Apparent power is greater than both Active and Reactive power
All are equal
32. Three equal resistor of 100 is connected in series across a source of Emf 30V. What would be the power consumed by each resistor?
10W
90W
30W
60W
33. If the power factor of a circuit is unity, its reactive power is-
a maximum
zero
quantity
equal to FR
34. One watt-hour is equal to-
360 Joule
300 Joule
3000 Joule
3600 Joule
35. What would be the charge of a capacitor 10μF when connected with 20V supply?
200μc
300μc
6200μc
30μc
36. Which resistor will be physically larger in size-
10Ω 50W
100Ω 10W
1ΜΩ 1W
1KΩ 1W
37. A capacitor opposes---
charge in current
charge in voltage
both charge in current and voltage
none
38. If positive phase sequence of 3-0 load is 'abc', the negative sequence is-
bac
cba
ach
all of the above
39. One Horse Power is equal to-
5.50 Foot pound/Second
55.00 Foot pound/Second
550 Foot pound/Second
5500 Foot pound/Second
40. What quantity of charage must be delivered by a battery with a potential difference of 100 V to do 500) of work?
5C
50C
0.5C
500C