Ques 21. Total capacitance between the points L and M in figure is: (SSC-2014, Set-1)
4.05 μF
1.45 μF
1.85 μF
2.05 μF
Answer.4. 2.05μF
Explanation:-
Total capacitance between point L and N
=2 + 1 = 3μF
Now total capacitance between L and O
= 1 + (3 x 2)/(3 + 2) = 2.2μF
Total capacitance Between L and M
= 1 + (2.2 x 2)/(2.2 + 2) = 2.05μF
Ques 22. What is the order of minimum displacement that can be measured with capacitive transducers (SSC-2014, Set-1)
10 m
1 cm
1mm
1 μm
Answer.4. 1 μm
Explanation:-
The capacitive transducer is used for measuring the displacement, pressure and other physical quantities. It is a passive transducer that means it requires external power for operation. The capacitors measure both the static and dynamic changes. The capacitive transducer uses for measurement of both the linear and angular displacement. It is extremely sensitive and used for the measurement of the very small distance of about 1 μm.
Ques 23. A resistance R is measured by the ammeter-voltmeter method. The voltmeter reading is 200 V and its internal resistance is 2 K. If the ammeter reading is found to be 2 A, then the value of R is (SSC-2014 Set-2)
105.3 Ω
100.0 Ω
95.3 Ω
90.3 Ω
Answer.1. 105.3 Ω
Explanation:-
The Value of voltmeter across Rx is given as
Ques 24. Find RAB for the circuit shown in the figure (SSC-2014 Set-2)
18Ω
30Ω
45Ω
68Ω
Answer.1. 18Ω
Explanation:-
When balanced, the Wheatstone bridge can be analyzed simply as two series strings in parallel, therefore, the current through the 50Ω resistor is zero. Hence the circuit become
RAB = 30Ω || 45Ω
= 30 x 45/ 30 + 45
= 18 Ω
Ques 25. The Q-factor of a parallel resonant circuit is given by (SSC-2014 Set-2)
Answer: None of the above, wrong option since the Q-factor of the parallel resonant circuit is R√C/L
Ques 26. In which of the following transformers, is the secondary winding always kept closed (SSC-2014 Set-2)
Current transformer
Potential transformer
Power transformer
Distribution transformer
Answer.1. Current transformer
Explanation:-
If the current transformer secondary is not shorted when unused and kept open then it can develop a very high voltage across secondary which may damage transformer insulation.
Ques 27. Two holes are drilled in the disc on a diameter of energy-meter to (SSC-2014 Set-2)
Increase ventilation
Reduce the weight of the disc
Eliminate creeping on no-load
Increase deflection torque
Answer.3. Eliminate creeping on no-load
Explanation:-
The slow but continuous rotation of the disc when only the pressure coils are excited but no current is flowing in the circuit is called “creeping”.
To overcome this creeping effect on no-load, two holes are drilled in the disc on a diameter, i.e. on opposite sides of the spindle. This causes sufficient distortion of the field to prevent rotation when one of the holes comes under one of the poles of the shunt magnet.
Ques 28. Which of the following instruments has the highest torque/weight ratio among the given instruments? (SSC-2014 Set-2)
Attraction type MI instrument
Repulsion type MI instrument
The permanent magnet moving coil instrument
Electrodynamometer instrument
Answer.3. The permanent magnet moving coil instrument
Explanation:-
Torque/weight ratio indicates Sensitivity. If a pointer is having less weight, it will be having a high torque/weight ratio so that even a very small deflection pointer starts moving and indicates measured value.
The permanent magnet moving coil instrument (PMMC) has the highest torque/weight ratio.
Ques 29. If the current through the operating coil of a moving iron instrument is doubled, the operation force becomes (SSC-2014 Set-2)
One and a half times
2 times
3 times
4 times
Answer.4. 4 times
Explanation:-
The moving iron instrument are of two types
Attraction type
Repulsion type
The deflecting torque in both the instrument is proportional to the square of the current i.e
Deflecting torque ∝ ( current)2
Hence if the current is doubled the deflecting torque or operating force becomes four times
Ques 30. In moving iron instruments, the iron moves in the direction to cause (SSC-2014 Set-2)
Coil inductance to be constant
Mutual inductance to be minimum
Minimum reluctance path
The decrease in the flux passing through is
Answer.3. Minimum reluctance path
Explanation:-
In the moving iron instruments, vane made up of soft iron and high permeability steel because it can move in the magnetic field of the stationary coil carrying the current hence the iron vane always try to adjust along the minimum reluctance path.
