BSNL JTO (Junior Telecom Officers) Electrical Engg. paper

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

When the transmission parameters of the following network are A = C = 1, B = 2 and D = 3 then the value of Zin is –
a) 3W
b) 4W

While calculating Rth, constant current sources in the circuit are –
a) replaced by opens
b) replaced by ’shorts’
c) treated in parallel with other voltage sources
d) converted into equivalent voltage sources

Maxwell’s loop current method of solving electrical networks –
a) uses branch currents
b) utilizes kirchhoff’s voltage law
c) is confined to single-loop circuits
d) is a network reduction method

A transmission line of characteristic impedance Z0 = 50 ohms, phase velocity Vp = 2 x 108 m/s and length l = 1m is terminated by a load ZL= ( 30 – j 40 ) ohms. The input impedance of the line for a frequency of 100 MHz will be
a)(30 + j40 ) ohms
b)( 30 – j40 ) ohms
c)(50 + j40 ) ohms
d)(50 – j40 ) ohms

For an elliptically polarized wave incident on the interface of a dielectric at the Brewster angle then the reflected wave will be-
a) Elliptically polarized
b) Linearly polarized
c) Right circularly polarized
d) Left circularly polarized

A yagi antenna has a driven antenna-
a) Only
b) With a reflector
c) With one or more directors
d) With a reflector and one or more directors

The number of lobes on each side of a 3l resonant antenna is –
a) 3
b) 6
c) 2
d) 1

The electric field intensity of a Hertizian dipole at a remote point varies as -
Radiation resistance of a half wave folded dipole is -
a) 72 W
b) 144W
c) 288 W
d) 216W

When a carrier wave is modulated at 100% it’s power is increased by -
a)100%
b)150 %
c)50%
d)0%

On a clear sky day, the atmospheric radio noise is strongest -
a) During morning hours
b) Around mid-day
c) During nights
d) In the afternoon

TV broadcasting system in India is as per CCIR -
a) System B
b) System I
c) System M
d) System X

For the safety measurement of the internal resistance of a 25-0-25 mA meter, a laboratory multimeter whose sensitivity is equal to –
a) 1k ohm/volt can be used
b) 10 k ohm/volt can be used
c) 100 k ohm/volt can be used
d) 200 k ohm/volt can be used

In order to measure moisture in wood the most suitable method is –
a) Electrical conduction
b) Electrical – capacitive
c) Absorption of radiation
d) Equilirium- moisture vs humidity

The flow rate of electrically conducting liquid without any suspended particle cannot be measured by –
a) turbine flow meters
b) electromagnetic flow meters
c) ultrasonic flow meters
d) thermistor based heat loss flow meters

The most useful transducer for displacement sensing with excellent sensitivity, linearity and resolution is –
a) an incremental encoder
b) an abosolute encoder
c) LVDT
d) a strain gauge

When variable reluctance type tachometer has 150 teeth on the rotor & the counter records 13,500 pulses per second then the rotational speed will be–
a) 4800 rpm
b) 5400 rpm
c) 6000 rpm
d) 7200 rpm.

41. On a voltage scale, zero dB m in a 600-ohm system could refer to –
a) 1.732 V
b) 1.0 V
c) 0.7746 V
d) 0.5V

One of the following devices which is required in addition in order to measure pressure using LVDT is-
a) strain gauge
b) pitot tube
c) Bourden tube
d) Rotameter

It is required to measure temperature in the range of 13000 C to 15000 c) The most suitable thermocouple to be used as a transducer would be –
a) chromel - constantan
b) Iron - constantan
c) chromel - alumel
d) platinum- rhodium

In a CSI if frequency of output voltage is f Hz, then frequency of input voltage to CSI is-
a) f
b) 2 f
c) f/2
d) 3 f

Identify the type of chipper in the given circuit
a) Type A chopper
b) Type B chopper
c) Type C chopper
d) Type D chopper

Maximum value of charging resistance in an UJT is associated with-
a) peak point
b) valley point
c) any point between peak and valley
d) after the valley point

Thyristor A has rated gate current of 2A and thyristor B a rated gate current of 100 mA-
a) A is a GTO and B is a conventional SCR
b) B is a GTO and A is a conventional SCR
c) B may operate as a transistor
d) none of the above

In a 3 phase full converter, the output voltage during overlap is equal to-
a) zero
b) source voltage
c) source voltage minus the inductance drop
d) average value of the conducting phase voltages

Mark old the correct statement for Cycloconverters-
a) step-down Cycloconverter (CC) works on natural commutation
b) step up CC requires no forced commutation
c) load commutated CC works on line commutation
d) none of the above

In the RF amplifier stage cascade (CE-CB) amplifier is used because it gives-
a) Large voltage gain
b) Low output impedance
c) Large isolation between the input and the output
d) None of the above

Silicon diode is less suited for low voltage rectifier operation because-
a) it can withstand high temperature
b) ensures low PIV of the diodes
c) ensures lower values of capacitance in the filter
d) reduces ripple content

An amplifier of class A is that in which -
a) Base is biased to cut – off
b) Ic flows most of the time
c) Ie flows all the time
d) Vc often raises to Vcc

A transistor is in active region when-
a) IB = bIC
b) IC=bIB
c) IC=IE
d) IC=IB

For coupling purposes in RF amplifier a buffer amplifier is used because it provides-
a) Maximum loading and minimum mismatch
b) Minimum loading and minimum mismatch
c) Maximum loading and maximum mismatch
d) Minimum loading and maximum mismatch

A transistor has CE parameter as hie = 10kW, hre =20 x 10-4 , hse = 100, hoe = 25 ms. The hib for this transistor will be-
a) 100 W
b) 99.01 W
c) 5m W
d) 101kW

A FM radio receiver is tuned to a 90.6 MHz broadcast station. It will receive an image frequency of -
a) 110 MHz
b) 112 Hz
c) 114 MHz
d) 120 MHz

In the given fig RL is shorted out, then VCE will become-
a) OV
b) VCC – IBRB
c) Equal to VCC
d) None of the above