From the diagram above, calculate the energy stored in the capacitor
4.0 x 10\(^{-2}\)J
4.0 x 10\(^{-4}\)J
8.0 x 10\(^{-4}\)J
8.0 x 10\(^{-2}\)J
Correct answer is B
c = 8µF, v = 10v
Energy stored = \(\frac{1}{2}\) cv2
= \(\frac{1}{2}\) × (8 × 10− 6) × 102
= 4 × 10\(^{-4}\)
How can energy loss be minimized through Eddy-current?
By using high resistance wire
By using insulated soft iron wires
By using low resistance wires
By using turns of wires
Correct answer is A
Eddy currents are produced by the varying flux cathode, the iron core of an equipment thus reducing efficiency due to power consumption. It can be reduced by laminating the core by breaking up the path of eddy current or by increasing the resistance of the core
Usage of insulated soft iron wire is to reduce hysteresis loss
Usage of low resistance wire (thick wire) is to reduce I2R loss
Usage of thick wire is to reduce leakage heat loss due to leakage of magnetic flux
Thus the correct answer is to use high resistance wire or thin wire
0.04m
0.12m
0.01m
0.08m
Correct answer is D
From Hoke's Law, F = ke, K = Constant of Force
For he first case, Force = mg,
= 0.8 × 10 = 8N
∴ 8 = k × 0.04
k = \(\frac{8}{0.04}\)
= \(\frac{200N}{m}\)
Since K is constant
For the second case, F = ke
F = 200 × e
∴ e = \(\frac{F}{200}\)
= \(\frac{16}{200}\)
= 0.08m
Determine the focal length of a thin converging lens if the power is 5.0 dioptres
0.1 m
0.2 m
2.0 m
2.5 m
Correct answer is B
Power of a lens = \(\frac{1}{f}\)
f = focal length
f = \(\frac{1}{p}\)
= \(\frac{1}{5}\)
= 0.2m
Which of the following is a scalar quantity?
Tension
Weight
Impulse
Mass
Correct answer is D
Scalar quantity is a quantity with only magnitude, it has no direction
Tension, weight, impulse are vector quantities because they have direction. Mass is the only scalar quantity there
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