Sunday, March 4, 2012

RRB Junior engineer(electrical) Model Questions

1. A resistance of 10 ohm is connected across a supply of 200V. If resistance R is now connected in parallel with a 10 ohm resistance, the current drawn from the supply gets doubled. The value of unknown resistance R is
(a) 5 ohm
(b) 20 ohm
(c) 10 ohm
(d) 15 ohm
Ans : c
2. Kirchhoff’s first law is also called as
(a) voltage law
(b) Current law
(c) Mesh Current law
(d) All the above
Ans : b
3. Find the total resistance when four 3 Ohm resistance are connected in series
(a) 3 ohm
(b) 12 ohm
(c) 14 ohm
(d) 8 ohm
Ans : b
4. The practical unit of power is
(a) Joule
(b) Ampere
(c) Watt
(d) Weber
Ans : c
5. Form factor of a sine wave is
(a) 1.414
(b) 1
(c) 0
(d) 1.11
Ans : d
6. The unit of resistance is
(a) Mho
(b) ohm-m
(c) Ohms
(d) Amps
Ans :c
7. Unit of impedance is
(a) Ampere
(b) Volt
(c) Ohm
(d) mho
Ans : c
8. The close path of the flux around any current carrying circuit is referred as
(a) Magnetic
(b) Electric
(c) Electromagnetic
(d) None of these
Ans : a
9. The current flowing in an electrical circuit is due to the existence of
(a) mmf
(b) emf
(c) Resistance
(d) Reluctance
Ans : b
10. The magnetic flux flow through a magnetic circuit is due to
(a) mmf
(b) emf
(c) Resistance
(d) Reluctance
Ans : a
11. The on-line UPS is also called as
a. Stand-by UPS
b. Line Interactive UPS
c. Off line UPS
d. Current line UPS
Ans. b
12. ________ is used to convert alternating current to direct current.
a. Transformer
b. Diode
c. Resistor
d. Transistor
Ans. b
13. The supply voltage varies sinusoid ally and has a frequency __________ Hz.
a. 60
b. 50
c. 20
d. 10
Ans. b
14. Expression for magneto-motive force is
(a) N/I
(b) 1/NI
(c) I/N
(d) IN
Ans : d
15. Unit of mmf is
(a) Ampere /Volt
(b) Ampere- turns
(c) Volt
(d) Volt/Ampere
Ans : b
16. Magnetic field strength is equal to
(a) mmf. L
(b) L/ mmf
(c) mmf/ L
(d) 1/mmf.L
Ans : c
17. Peak inverse voltage of bridge rectifier is as that of centre-tap circuit.
a. Same
b. Twice
c. Half
d. Four times
Ans. c
18. Peak Resistance of the diode is increased when
a. Forward biased
b. Reverse biased
c. Both forward and reverse biased
d. Either a or b
Ans. b
19. The number of lines of force passing through the secondary coil S when unit current changes in the primary coil P are called
(a) Self inductance
(b) Mutual inductance
(c) Self induction
(d) Mutual induction
Ans : c
20. Unit of flux
(a) Amp- turns
(b) Weber
(c) Volts
(d) Amps
Ans : b

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