A long solenoid with $$15$$ turns per cm has a small loop of area $$2.0$$ cm2 placed inside the solenoid normal to its axis. If the current carried by the solenoid changes steadily from $$2.0$$ A to $$4.0$$ A in $$0.1$$ s, what is the induced emf in the loop while the current is changing?

 1 $$7.5 \times 10^{-6}~ \text{V}$$ 2 $$6.5 \times 10^{-6}~\text{V}$$ 3 $$7.5 \times 10^{-5}~\text{V}$$ 4 $$6.5 \times 10^{-5}~\text{V}$$
Subtopic:  Faraday's Law & Lenz Law |
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It is desired to measure the magnitude of the field between the poles of a powerful loudspeaker magnet. A small flat search coil of area  with 25 closely wound turns, is positioned normal to the field direction, and then quickly snatched out of the field region. Equivalently, one can give it a quick 90° turn to bring its plane parallel to the field direction). The total charge flown in the coil (measured by a ballistic galvanometer connected to the coil) is 7.5 mC. The combined resistance of the coil and the galvanometer is 0.50 $\Omega$. The field strength of the magnet is:

1. 0.55 T
2. 0.75 T
3. 0.67 T
4. 0.49 T

Subtopic:  Faraday's Law & Lenz Law |
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