Question: Q. 4. The magnetic field through a single loop of wire, 12 cm in radius and 8.5Ω resistance, changes with time as shown in the figure. The magnetic field is perpendicular to the plane of the loop. Plot induced current as a function of time.

A [CBSE SQP 2015]

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Solution:

Ans.

ε=dϕdt =πR2×dBdt =227×(0.12)2×12 ε=0.023 V I=εR =2.7 mA for 0<t<2 s.

Similarly :

0<t<2 s 2<t<4 s 4<t<6 s
ε(V) -0.023 0 +0.023
I(mA) -2.7 0 +2.7

[AI Q. 5. A rectangular conductor LMNO is placed in a uniform magnetic field of 0.5 T. The field is directed perpendicular to the plane of the conductor.

When the arm MN of length of 20 cm is moved towards left with a velocity of 10 ms1, calculate the emf induced in the arm. Given the resistance of the arm to be 5Ω (assuming that other arms are of negligible resistance) find the value of the current in the arm.

A [O.D. I, II, III 2013]

Ans. Let ON be at some point x.

The emf induced in the loop =ε

ε=dϕdt=d( Blx)dt=Blv =0.5×0.2×10=1 V

Current in the arm,

(1)I=εR=15=0.2 A



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