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

Answer:

The value of G12 or v2/v1 for the circuit shown in the fig. is -

Answer:

The two port network of the fig. shown has open circuit impedance parameters given by matrix -

Answer:

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
Answer: a)

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
Answer: b)

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
Answer: b)

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
Answer: b)

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

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

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
Answer: c)

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

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
Answer: d)

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
Answer: a)

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
Answer: d)

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
Answer: c)

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.
Answer: b)

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
Answer: b)

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
Answer: c)

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
Answer: d)

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
Answer: b)

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
Answer: b)

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
Answer: a)

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
Answer: a)

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
Answer: d)

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
Answer: a)

In a 3 phase full converter if load current is I and ripple free, then average thyristor current is-
a)
b)
c)
d)
Answer: b)1/3(I)
BSNL JTO EXAM 2008 Syllabus is here