BHEL Placement Paper

                               BHEL Placement Paper - Electronics & Electrical

1. When a inductive coil connected to a 200 V, 50Hz ac supply with 10A current flowing through it dissipates 1000 watts then which of the following will have least value in ohms
a.) Resistance
b.) Reactance
c.) Impedance 
d.) None

2. Oscillator crystal are made of –
a.) Silicon
b.) Germanium
c.) Quartz
d.) None

3. For small size, high frequency coils, the most common core material is-
a. )Air
b. )Ferrite 
c.) Powdered ion
d.) Steel

4. The Q of a radio coil –
a.) is independent of frequency
b.) increases monotonically as frequency increases 
c.) decreases monotonically as frequency increases
d.) increases upto a certain frequency and then decreases beyond that frequency

5. A superconductor is a –
a.) A material showing perfect conductivity and Meissner effect below a critical temperature
b.) A conductor having zero resistance
c.) A perfect conductor with highest di-magnetic susceptibility
d.) A perfect conductor which becomes resistance when the current density through it exceeds a critical value

6. When an inductor tunes at 200 KHz with 624 pF capacitor and at 600 KHz with 60.4 pF capacitor then the self capacitance of the inductor would be –
a) 8.05 pF
b) 10.05pF
c.) 16.01pF
d.) 20.01pF

7. Sparking occur when a load is switched off because the circuit has high –
a.) Inductance
b.) Capacitance
c.) Resistance
d.) None

8. Sparking between contacts can be reduced by inserting a –
a.) Resistance in the line
b.) Capacitor in series with contacts
c.) Capacitor in parallel with contacts
d.) None

9. amplifier of an A.M. receiver is normally biased in –
a.) Class ‘A’
b.) Class ‘b’
c.) Class ‘C’
d.) None

10. The value of gate voltage for the operation of enhancement of only N channel MOSFET has to be –
a.) High positive
b.) High negative
c.) Low positive
d.) Zero

11. The input gate current of a FET is –
a.) a few microamperes
b.) negligibly small
c.) a few milliamperes
d.) a few amperes

12. A step recovery diode –
a.) has on extremely short recovery time
b.) conducts equally well in both directions
c.) is mainly used as a harmonic generator
d.) is an ideal rectifiers of high frequency signals

13. In order to get maximum undistorted output signal from CE amplifier with VCC 10V, the value of VCE (Q) should be approximately-
a.) 0.1V
b.) 5V
c.) 10V
d) V

14. In a FET the electrode, which corresponds to collector in bipolar transistor, is –
a.) source
b.) drain
c.) gate
d.) none

15. The device which acts like an NPN and a PNP transistor connected base to base and emitter to collector is –
a.) Triacb
b.) UJT 
c.) Diac
d.) SCR

16. A typical optical fibre has –
a.) High refractive index core and low refractive index cladding
b.) Low refractive index core and high refractive index cladding
c.) Both a and b
d.) None

17. The circuit symbol for a GTO is

18. Which of the following statement is true about two wattmeter method for power measurement in three phase current ?
a.) power can be measured using two wattmeter method only for star connected three phase circuits.
b.) when two meter show indentical readings, in the power factor is 0.5. 
c.) when power factor is unit, one of the wattmeter reads zero
d.) when the reading of the two wattmeters are equal but of opposite sign, then the power factor is zero 

19. In the lattice network, the value of R for the maximum power transfer to the load – 
a.) 5 
b.) 6.5
c.) 8
d.) 9

20. The approximate thickness of the radome wall should be –
a.) l
b.) l/4 
c.) l/2
d.) l/8

21. A relatively permanent information is stored in
a. ) ROM
b.) RAM
c.) PROM
d.) Volatile memory

22. The electric field line and equipotential lines-
a.) Are parallel to each other
b.)Are one and same
c.) Cut each other orthogonally
d.)Can be inclined to each other at any angle

23. The directions of and in TEM mode transmission line with respect to the direction of propagation are-
a.) Both and are transverse to the direction of propagation
b.) is and are transverse and h has a component in the direction of propagation
c.) is entirely transverse and has a component in the direction of propagation
d. ) is entirely transverse and has a component in the direction of propagation

24. For a lossy transmission line short circuited at the receiving end, the input impedance is given by (When Z0 is the characteristic impendence g is the propagation constant and L is the length of the line .When two equal positive point charges are placed along X- axis at X1 and –X1 respectively then the electric field vector at a point P on the positive Y-axis will be directed-
a.) In the +x direction
b.) In the –x direction
c. ) In the +y direction
d.) In the –y direction

25. Joule/coulomb is the unit of – 
a.) Electric field potential 
b.) Potential 
c .) Charge
d.) None of the above