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Question 11 Mark
Two circular loops are placed with their centres separated by a fixed distance. How would you orient the loops to have:
  1. The largest mutual inductance.
  2. The smallest mutual inductance?
Answer
  1. When the loops have their axis at 0' the mutual inductance is maximum.
  2. When loops have their axis at 90' then their inductance is minimum.
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Question 21 Mark
Consider the self-inductance per unit length of a solenoid at its centre and that near its ends. Which of the two is greater?
Answer
Self inductance depends upon length of solenoid.
As inductance is greater at center as induction at center is due to both ends.
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Question 31 Mark
A metallic metre stick moves with a velocity of $2m/s^{-1}$ in a direction perpendicular to its length and perpendicular to a uniform magnetic field of magnitude 0.2 T. Find the emf induced between the ends of the stick.
Answer
l = 1m, B = 0.2T, v = 2m/s, e = Blv
= 0.2 × 1 × 2 = 0.4V
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Question 41 Mark
If the magnetic field outside a copper box is suddenly changed, what happens to the magnetic field inside the box? Such low-resistivity metals are used to form enclosures which shield objects inside them against varying magnetic fields.
Answer
Current on its surface changes but no magnetic feild passes through it as magnetic field inside the copper box is zero.
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Question 51 Mark
Consider the energy density in a solenoid at its centre and that near its ends. Which of the two is greater?
Answer
Energy density at center is greater than ends.
So as solenoid tries to reserve its energy at center thus it opposes any change in energy.
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Question 61 Mark
A metallic bob A oscillates through the space between the poles of an electromagnet. The oscillations are more quickly damped when the circuit is on, as compared to the case when the circuit is off. Explain.
Answer
When circuit is on the bob will get induced due to magnetic field as it will get attracted towards magnets each time it will move away from its mean position and thus attracted towards mean position. thus its motion is damped more quickly.
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