BSNL JTO Recruitment Test Paper Pattern Set 2

1. The depth of penetration or skin depth for an electromagnetic field of frequency ‘f’ in a conductor of resistivity r and permeability m is-
a) inversely proportional to r and f and directly proportional to m
b) directly proportional to r and inversely proportional to f and m
c) directly proportional to f and inversely proportional to r and m
d) inversely proportional to r and m and directly proportional to f

2. When an antenna has a gain of 44dB then assuming that the main beam of the antenna is circular in cross-section the beam width will be –
a) 0.4456 0
b) 1.44560
c) 2.44560
d) 3.44560

3. Lens antennas used for microwaves are usually made of –
a) Polystyrene
b) Glass of low refractive index
c) Paraboloid surfaces
d) Dielectric media having large refractive index

4. One of the following types of instrument which is an electrometer is –
a) Electrodynamometer
b) PMMC
c) Electrostatic
d) Moving iron

5. When an ac current of 5A and dc current of 5A flow simultaneously through a circuit then which of the following statement is true ?
a) An ac ammeter will read less than 10A but more than 5A
b) An ac ammeter will read only 5A
c) A dc ammeter will read 10A
d) A dc ammeter will read zero

6. When Q factor of a circuit is high, then –
a) power factor of the circuit is high
b) impedance of the circuit is high
c) bandwidth is large
d) none of these

7. The resolution of a logic analyser is –
a) the maximum number of input channels
b) the minimum duration of the glitch it can capture
c) it’s internal clock period
d) the minimum amplitude of input signal it can display

8. A memoryless system is –
a) causal
b) not causal
c) nothing can be said
d) none

9. An air capacitor is a –
a) time variant
b) active device
c) time invariant
d) time invariant and passive device

10. Thermistors are made of –
a) pure metals
b) pure insulators
c) sintered mixtures of metallic oxides
d) pure semiconductor

11. Pirani gauge is used to measure –
a) very low pressures
b) high pressures
c) pressures in the region of 1 atm
d) fluid flow

12. These circuits converts input power at one frequency to output power at a different frequency through one stage conversion –
a) AC voltage controllers
b) Cyclo converters
c) Phase controlled rectifiers
d) Inverters

13. In a forward voltage Triggering thyristor changes from –
a) off state to on state
b) on state to off state
c) on state to on state
d) off state to off state

14. A thyristor, when triggered, will change from forward blocking state to conduction state if its anode to cathode voltage is equal to –
a) peak repetitive off state forward voltage
b) peak working off state forward voltage
c) peak working off state reverse voltage
d) peak non-repetitive off state forward voltage

15. Gate characteristic of a thyristor-
a) is a straight line passing through origin
b) is of the type Vg = a + bIg
c) is a curve between Vg and Ig
d) has a spread between two curves of Vg – Ig

16. A four quadrant operation requires-
a) two full converters in series
b) two full converters connected back to back
c) two full converters connected in parallel
d) two semi converters connected back to back

17. If for a single phase half bridge inverter, the amplitude of output voltage is Vs and the output power is P, then their corresponding values for a single phase full bridge inverter are –
a) Vs, P
b) Vs/2, P
c) 2Vs, 2P
d) 2Vs, P

18. In an enhancement type MOSFET the output V-I characteristics has –
a) only an ohmic region
b) only a saturation region
c) only ohmic region at 10 W voltage value followed by a saturation region at higher voltages
d)an ohmic region at large voltage values preceded by a saturation region at lower voltages

19. The energy gap in a semiconductor –
a) increases with temperature
b) remains constant
c) slightly increase with temperature
d) decrease with temperature

20. In an electronic circuit matching means –
a) connecting a high impedance directly to low impedance
b) selection of components which are compatible
c) transferring maximum amount of signal between different kinds of circuits.
d) RC coupled stages

21. P channel FETs are less superior than N channel FETs because
a) They have higher input impedance
b) They have high switching time
c) They consume less power
d) Mobility of electrons is greater than that of holes

22. Small increase in temperature in the CE connected transistor is the –
a) Increase in ICEO
b) Increase in ac current gain
c) Decrease in ac current gain
d) Increase in output resistance

23. An amplifier has a band width of 20 KHz and a midband gain of 50 without feedback. If a negative feedback of 1% is applied then bandwidth with feedback is –
a) 13. 3 KHz
b) 30KHz
c) 10KHz
d) 40KHz

24. The output of a class B amplifier –
a) is distortion free
b) consists of positive half cycles only
c) is like the output of a full wave rectifier
d) comprises short duration current pulses

25. An amplifier with negative feedback –
a) lowers its lower 3 dB frequency
b) raises its upper 3 dB frequency
c) increases its bandwidth
d) all of the above

26. What changes would be necessary in block C if FM signals are to be received –
a) Block becomes redundant
b) A FM detector would be required
c) A high frequency signal generator
d) An additional local oscillator will be needed

27. The main disadvantage of Diode-Transistor logic (DTL) is its-
a) greater speed
b) slower speed
c) average speed
d) none of the above

28. Time delay Dt in digital signals in an SIS O shift register is given by –
a) Dt = N ´ Fc
b) Dt = N ´ 1/Fc
c) Dt = 1/N ´ Fc
d) Dt = N ¸ 1/Fc

29. The output Qn is 1 in a JK flip flop and it does not change when clock pulse is applied) The possible combination of Jn and Kn can be – (y denotes don’t care)
a) y and 0
b) y and 1
c) 0 and y
d) 1 and y