1
JEE Main 2017 (Online) 8th April Morning Slot
+4
-1
A small circular loop of wire of radius a is located at the centre of a much larger circular wire loop of radius b. The two loops are in the same plane. The outer loop of radius b carries an alternating current I = Io cos ($$\omega$$t). The emf induced in the smaller inner loop is nearly :
A
$${{\pi {\mu _o}{I_o}} \over 2}.{{{a^2}} \over b}\,\omega \sin \left( {\omega t} \right)$$
B
$${{\pi {\mu _o}{I_o}} \over 2}.{{{a^2}} \over b}\,\omega \cos \left( {\omega t} \right)$$
C
$$\pi {\mu _o}{I_o}\,{{{a^2}} \over b}\omega \sin \left( {\omega t} \right)$$
D
$${{\pi {\mu _o}{I_o}\,{b^2}} \over a}\omega \cos \left( {\omega t} \right)$$
2
JEE Main 2017 (Offline)
+4
-1
In a coil of resistance 100 $$\Omega$$, a current is induced by changing the magnetic flux through it as shown in the figure. The magnitude of change in flux through the coil is:

A
275 Wb
B
200 Wb
C
225 Wb
D
250 Wb
3
JEE Main 2016 (Online) 10th April Morning Slot
+4
-1
A conducting metal circular-wire-loop of radius r is placed perpendicular to a magnetic field which varies with time as
B = B0e$${^{{{ - t} \over r}}}$$ , where B0 and $$\tau$$ are constants, at time t = 0. If the resistance of the loop is R then the heat generated in the loop after a long time (t $$\to$$ $$\infty$$) is :
A
$${{{\pi ^2}{r^4}B_0^4} \over {2\tau R}}$$
B
$${{{\pi ^2}{r^4}B_0^2} \over {2\tau R}}$$
C
$${{{\pi ^2}{r^4}B_0^2R} \over \tau }$$
D
$${{{\pi ^2}{r^4}B_0^2} \over {\tau R}}$$
4
JEE Main 2016 (Online) 10th April Morning Slot
+4
-1
Consider an electromagnetic wave propagating in vacuum. Choose the correct statement :
A
For an electromagnetic wave propagating in +x direction the electric field is $$\vec E = {1 \over {\sqrt 2 }}{E_{yz}}{\mkern 1mu} \left( {x,t} \right)\left( {\hat y - \hat z} \right)$$

and the magnetic field is $$\vec B = {1 \over {\sqrt 2 }}{B_{yz}}{\mkern 1mu} \left( {x,t} \right)\left( {\hat y + \hat z} \right)$$
B
For an electromagnetic wave propagating in +x direction the electric field is $$\vec E = {1 \over {\sqrt 2 }}{E_{yz{\mkern 1mu} }}\left( {y,z,t} \right)\left( {\hat y + \hat z} \right)$$

and the magnetic field is $$\vec B = {1 \over {\sqrt 2 }}{B_{yz{\mkern 1mu} }}\left( {y,z,t} \right)\left( {\hat y + \hat z} \right)$$
C
For an electromagnetic wave propagating in + y direction the electric field is $$\overrightarrow E = {1 \over {\sqrt 2 }}{E_{yz{\mkern 1mu} }}\left( {x,t} \right)\widehat y$$
and the magnetic field is $$\vec B = {1 \over {\sqrt 2 }}{B_{yz{\mkern 1mu} }}\left( {x,t} \right)\widehat z$$
D
For an electromagnetic wave propagating in + y direction the electric field is $$\overrightarrow E = {1 \over {\sqrt 2 }}{E_{yz{\mkern 1mu} }}\left( {x,t} \right)\widehat z$$
and the magnetic field is $$\overrightarrow B = {1 \over {\sqrt 2 }}{B_{z{\mkern 1mu} }}\left( {x,t} \right)\widehat y$$
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Physics
Mechanics
Electricity
Optics
Modern Physics
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