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A cube of edge a has its edges parallel to x, y and z-axis of rectangular coordinate system. A uniform electric field \mathrm{\overrightarrow{\mathrm{E}}} is parallel to y-axis and a uniform magnetic field is \mathrm{\overrightarrow{\mathrm{E}}} parallel to x-axis. The rate at which flows through each face of the cube is

Option: 1

\mathrm{ \frac{a^2 \cdot E B}{2 \mu_0} \text { parallel to } x-y \text { plane and zero in others } }


Option: 2

\mathrm{\frac{a^2 E B}{\mu_0} \text { parallel to } x-y \text { plane and zero in others }}


Option: 3

\mathrm{\frac{a^2 E B}{2 \mu_0} \text { from all faces }}


Option: 4

\mathrm{\frac{a^2 E B}{2 \mu_0} \text { parallel; to } y-z \text { faces and zero in others }}


Answers (1)

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Energy flowing per sec per unit area from a face is = \mathrm{\frac{1}{\mu_0} }   \mathrm{[\overrightarrow{\mathbf{E}} \times \overrightarrow{\mathbf{B}}] }.

It will be in the negative z-direction. It shows that the energy will be flowing infaces parallel to x-y plane and is zero in all other faces. Total energy flowing per second from a face in x-y plane 
\mathrm{=\frac{1}{\mu_0}\left(E B \sin 90^{\circ}\right) a^2=\frac{E B a^2}{\mu_0}] }

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Ritika Jonwal

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