JEE PHYSICS MCQ: ELECTRO MAGNETIC INDUCTION

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Analyzing +4 | -1

Assertion: A thin aluminum disc, spinning freely about a central pivot, is quickly brought to rest when placed between the poles of a strong

U

-shaped magnet.

Reason: A current induced in a disc rotating in a magnetic field produces a torque which tends to oppose the disc's motion.

View answer and explanation

Correct option: B

If both Assertion & Reason are True but Reason is not a correct explanation of the Assertion.

Option B is correct because both the assertion and reason are true, but the reason is not a complete explanation of the assertion. Eddy currents are the primary cause.

More Questions from ELECTRO MAGNETIC INDUCTION

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The current in a long solenoid of radius

R

and having

n

turns per unit length is given by

i=i_0 \sin \omega t

. A coil having

N

turns is wound around it near the centre. Find the induced emf in the coil. The induced emf can be produced in a coil by

A. moving the coil with uniform speed inside
uniform magnetic field

B. moving the coil with non uniform speed inside
uniform magnetic field

C. rotating the coil inside the uniform magnetic
field

D. changing the area of the coil inside the uniform
magnetic field

Choose the correct answer from the options given
below: An inductance coil have the time constant

4 \mathrm{sec}

, if it is cut into two equal parts and connected parallel then new time constant of the circuit- If the coils of a transformer are made up of thick wire, then A loop of area

0.1\,\,{m^2}

rotates with a speed of

\mathrm{60}

rps perpendicular to a magnetic field of

\mathrm{0}\mathrm{.4}\,\,\mathrm{T}

. If there are

\mathrm{100}

turns in the loop, maximum voltage induced in the loop is A

\mathrm{50}\,\,\mathrm{mH}

coil carries a current of

\mathrm{2 A}

, the energy stored in joule is