MCQ
6441. RMS value of the instantaneous ac voltage V = 300 is-
300x√2
300/√2
300x√3
300/√3
6442. For Y-connection under balanced condition the line to line voltage is-
same as the phase voltage
√3 times the phase voltage
√2 times the phase voltage
none of the above
6443. In a series R.L circuit, voltage across resistor inductor are 3V and 4V respectively, then what is the applied voltage?
7V
4V
5V
3V
6444. Which of the following connections is best suited for 3-phase, 4-wire service?
Δ-Δ
Y-Y
Δ-Υ
Y-A
6445. The average value of a sinusoidal current is 100A. Its rms value is-
70.7A
63.7A
141.4A
111A
6446. At parallel resonance the circuit impedance equals to-
L/CR
LC/R
RL/C
CR/L
6447. One Horse Power is equal to-
5.50 Foot pound/Second
55.00 Foot pound/Second
550 Foot pound/Second
5500 Foot pound/Second
6448. The unit of inductance—
Inducta
henry
inductive reactance
ohm
6449. Inductance opposes --in current in a circuit
only increase
change
only decrease
none of the above
6450. 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
6451. The power factor of an ordinary electric bulb is--
Zero
Unity
Slightly more than zero
Slightly less than unity
6452. If a phase is multiplied by j, then –
only its magnitude changes
only its direction changes
both magnitude & direction changes.
none of above
6453. 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
6454. Inductance opposes --in current in a circuit.
only increase
change
only decrease
none of the above
6455. At parallel resonance-
circuit impedance is minimum
power factor is zero
line current is maximum
power factor is unity
6456. Four capacitors each of 40µF are connected in parallel, the equivalent capacitance will be-
160µF
40µF
10µF
5µF
6457. The phase sequence of a three-phase system is RYB. The other possible phase sequence can be-
BRY
YRB
RBY
none of the above
6458. The capacitive reactance of a circuit is-frequency.
independent of
inversely proportional to
directly proportional to
none of the above
6459. Which of the following lamp has minimum initial cost of installation but maximum running cost?
incandescent
fluorescent
mercury vapour
sodium vapour
6460. What is the peak-to-peak value for 120V ac?
240V
339V
480V
391V