BSNL JTO Exam Paper 2005

When a piece of copper and another of germanium are cooled from room temperature to 800 K then the resistance of –
a) Each of them increases
b) Each of them decreases
c) Copper increases and germanium decreases
d) Copper decreases and germanium increases
Answer: d)
When a signal of 10 mV at 75 MHz is to be measured then which of the following instrument can be used –
a) VTVM
b) Cathode ray oscilloscope
c) Moving iron voltmeter
d) Digital multimeter
Answer: b)

When a sample of germanium and silicon having same impurity density are kept at room temperature then –
a) Both will have equal value of resistivity
b) Both will have equal value negative resistivity
c) Resistivity of germanium will be higher than that of silicon
d) Resistivity of silicon will be higher than that of germanium
Answer: d)

When an RC driving point impedance function has zeros at s= -2 and s=-5 then the admissible poles for the function would be –
a) s = 0; s = -6
b) s = 0; s = -3
c) s = 0; s = -1
d) s = -3; s = -4
Answer: b)

For the n-type semiconductor with n = Np and p = , the hole concentration will fall below the intrinsic value because some of the holes –
a) drop back to acceptor impurity states
b) drop to donor impurity states
c) Virtually leave the crystal
d) recombine with the electrons
Answer: d)

The location of lighting arrestor is –
a) Near the transformer
b) Near the circuit breaker
c) Away from the transformer
d) None

Time constant of an RC circuit increases if the value of the resistance is –
a) Increased
b) Decreased
c) Neither a nor b
d) Both a and b
Answer: a)

Telemetering is a method of –
a) Counting pulses sent over long distances
b) Transmitting pictures from one place to another
c) Transmitting information concerning a process over a distance
d) None
Answer: c)

When the gauge factor of a strain gauge is 2, stress is 1050 kg/cm2, Y = 2.1´ 106 kg/cm2 and R is 100 ohms then the value of DR will be –
a) 2W
b) 3W
c) 4W
d) 1W
Answer: d)

As the drain voltage is increased for a junction FET in the pinch off region then the drain current –
a) Becomes zero
b) Abruptly decreases
c) Abruptly increases
d) Remains constant
Answer: d)

11. One of the following, which is not a transducer in the true sense, is –
a) Thermocouple
b) Piezoelectric pick up
c) Photo-Voltaic cell
d) LCD
Answer: d)

When a transistor is required to match a 100W signal source with a high impedance output circuit then the connection that would be used is –

a) Common base
b) Common collector
c) Common emitter
d) Emitter follower
Answer: a)

In a JFET gates are always –
a) forward biased
b) reverse biased
c) unbiased
d) none
Answer: c)

The main factor which differentiate a DE MOSFET from an E only MOSFET is the absence of –
a) insulated gate
b) electrons
c) channel
d) P-N junction

An SCR conducts appreciable current when –
a) Anode and gate are both negative with respect to cathode
b) Anode and gate are both positive with respect to cathode
c) Anode is negative and gate is positive with respect to cathode
d) Gate is negative and anode is positive with respect to cathode

Silicon is not suitable for fabrication of light emitting diodes because it is –
a) An indirect band gap semiconductor
b) A direct band gap semiconductor
c) A wide band gap semiconductor
d) A narrow band gap semiconductor

An average responding rectifier type electronic ac voltmeter has its scale calibrated in terms of the rms value of a sine wave, when a square wave voltage of peak magnitude 100V is measured using this voltmeter then the reading indicated by the meter, will be –
a) 111V
b) 100V
c) 90.09V
d) 70.7V
Answer: b)

When a four terminal T network is inserted between a source and load resistance as shown in figure then the resistance seen by the source remain the same with or without the four terminal block when R is –

a) 5W
b) 10 W
c) 15 W
d) 20 W
Answer: a)

In the ac bridge shown in the given figure, the value of Rx and Cx at balance will be

Answer:

Which one of the following conditions for Z parameters would hold for a two port network containing linear bilateral passive circuit elements –
a) Z11 = Z22
b) Z12Z21 = Z11Z22
c) Z11Z12 = Z22Z21
d) Z12 = Z21
Answer: d)