At the frequency below resonance frequency, the current leads the voltage because capacitive reactance is greater than the inductive reactance. i.e XL > Xc. So the circuit acts as the capacitive circuit.
Ques 62. If the power factor is high, then the consumer maximum demands
Increase
Decrease✔
Becomes zero
Remains Constant
Kva=kw/cos$
Now considering the above equation, for a given requirement of kW, the value of kVA reduces if we have a good power factor.
Let us understand with an example,
Consider a case wherein we need 100 kW as output. Now
Case1: for a power factor of 0.8
We would require 120kva for fulfilling the required demand. (Calculated as per equation is written above)
Case2: power factor of 1 (unity)
Here, the value of kVA required is 100 kVA. Which is less than the previous case. This indicates that the kVA demand decreases if the power factor of my equipment increases.
Ques 63. The minimum area of cross-sections of a three and a half core cable should be?
50 cm2
40 cm2
30 cm2✔
60 cm2
The minimum area of cross sections of a three and a half core cable is 30 cm2
Ques 64. A CRO Screen has 10 divisions on a horizontal scale. If a voltage signal 5 sin (314t + 45º) is examined with a line base setting of 5 msec/div, the number of cycles of the signal displayed on the screen will be?
0.5 cycle
2.5 cycle✔
5 cycle
10 cycles
Voltage V = 5sin(314t + 45º)
Angular frequency (ω) = 314
ω = 2π/T
T = 2π/ω = 2π/314 = 0.02 msec
X scale of CRO = 5msec/division
Total X scale = 5/10 msec = 0.5 msec
Then the number if cycle of the waveform of the screen = total X scale/time
= 0.5/0.2 = 2.5 cycle
Ques 65. During the resistance welding, the heat produced at the joint is proportional to?
Ques 66. An RLC series circuit has R = 10Ω, L = 2H. What value of capacitance will make the circuit critically damped?
0.02 F
0.2 F
0.4 F
0.08 F✔
For critically damped RLC series circuit.
Ques 67. For cleat wiring and 250 volts supply, the cables will be placed _____ apart center to center for single-core cables.
4 cm
3 cm
4.5 cm
2.5 cm✔
This type of wiring is not used practical for permanent wiring and is only suitable for temporary wiring purposes such as for marriages with the advantages of saving labor and overall cost.
The cleat should be provided every 60 cm to avoid sag in the cables. Sharp bends should be avoided in the wiring and the spacing between the cleats should be reduced to prevent the from touching the wall and sagging. The distance between the cables should be 2.5 cm in the case of branch circuits and 4 cm apart in the case of sub-mains.
Ques 68. The error in current, the transformer can be reduced by designing them with
Using large cross-section for both primary and secondary windings conductors
High permeability and low core materials, avoiding any joints in the core and also keeping the flux density to a low value
Using primary and secondary winding as close to each other as possible
All of the above✔
Using a core of high permeability and low hysteresis loss magnetic materials.
Lowering the secondary internal impedance.
Ensuring minimum length of flux path and increasing cross-sectional area of the core, minimizing joint of the core.
Keeping the rated burden to the nearer value of the actual burden.
Ques 69. A primary cell has an EMF of 1.5 V. When short-circuited, it gives a current of 3 A. The internal resistance of the cell is?
0.5 ohms✔
0.2 ohms
2 ohms
4.5 ohms
When cell is short-circuited then the current in the cell is given by
I = R/V
R = V/I
= 1.5/3 = 0.5
Ques 70. What are the maximum number of points of light, fan, and socket outlets that can be connected in one sub-circuit?
4
12
6
10✔
According to Indian Electricity rules the connected load on any subcircuit consisting of tubes, fan, etc. should not exceed 800 W with maximum of 10 points.
