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21
Which of the following inductor will have the least eddy current losses?
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Answer: Option A
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22
Find the force acting on a conductor 3m long carrying a current of 50 amperes at right angles to a magnetic field having a flux density of 0.67 tesla
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Answer & Solution
Answer: Option A
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23
Both the number of turns and the core length of an inductive coil are doubled. Its self-inductance will be
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Answer: Option B
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24
The polarity of the induced voltage can be determined by using the left-hand generator rule.
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Answer: Option A
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25
A conductor 2 meters long moves at right angles to a magnetic field of flux density 1 tesla with a velocity of 12.5 m/s. The induced e.m.f. in the conductor will be
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Answer: Option C
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26
If current in a conductor increases then according to Lenz's law self-induced voltage will
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Answer: Option C
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27
Two coils have inductances of 8 mH and 18 mH and a coefficient of coupling of 0.5. If the two coils are connected in series aiding, the total inductance will be
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Answer & Solution
Answer: Option B
Solution:
Let's break down this problem to understand how to calculate the total inductance of two coils connected in series aiding!

First, let's define some key terms:
* Inductance (L): A coil's ability to store energy in a magnetic field, measured in Henries (H). In our case, L1 = 8 mH and L2 = 18 mH.
* Coefficient of Coupling (k): A number between 0 and 1 that describes how effectively the magnetic field of one coil links with the other. Here, k = 0.5. A value of 1 means perfect coupling.
* Mutual Inductance (M): The inductance due to the interaction of the magnetic fields of the two coils. It's how much one coil's current affects the voltage in the other coil.

The formula for Mutual Inductance (M) is: M = k * sqrt(L1 * L2)
Let's calculate M: M = 0.5 * sqrt(8 mH * 18 mH) = 0.5 * sqrt(144 mH²) = 0.5 * 12 mH = 6 mH

When coils are connected in series aiding (also known as series cumulative), their magnetic fields add up.
The formula for the total inductance (L_total) in series aiding is: L_total = L1 + L2 + 2M

Now, let's plug in the values: L_total = 8 mH + 18 mH + 2 * 6 mH = 8 mH + 18 mH + 12 mH = 38 mH

Therefore, the total inductance will be 38 mH. The correct answer is Option B.
28
Two coils have self-inductances of 10 H and 2 H, the mutual inductance being zero. If the two coils are connected in series, the total inductance will be
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Answer: Option C
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29
A coil is wound on iron core which carries current I. The self-induced voltage in the coil is not affected by
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Answer: Option B
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30
Mutually inductance between two magnetically coupled coils depends on
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Answer: Option D
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