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An infinetly long wire carrying a current I(t)= I_0 \cos (\omega t)  is placed at a distance 'a' from a square loop of side 'a'  as shown in the figure .

If the resistance of the loop is R , Then power dissipated in loop is 

Option: 1

\frac{\mu _0^{2}}{4 \pi ^2 R}\times a^2 I_{0}^{2}w^{2}\sin ^{2}(wt)(log 2)^{2}


Option: 2

\frac{\mu _0}{2 \pi R}\times a I_{0}w\sin wt(log 2)


Option: 3

\frac{\mu _0^{2}}{4 \pi ^2 }\times a^2 I_{0}^{2}w^{2}\sin ^{2}(wt)(log 2)^{2}


Option: 4

\frac{\mu _0}{2 \pi }\times a I_{0}w\sin (wt)(log 2)


Answers (1)

best_answer

As we have learned

Induced Power -

P= \frac{\varepsilon ^{2}}{R}= \frac{N^{2}}{R}\left ( \frac{d\phi }{dt} \right )^{2}

- wherein

It depends on time and resistance

 

 

Consider a stirp of width dx at a distance x from the current carrying wire , the magnetic field at distance x is B = \frac{\mu _0 I(t)}{2\pi x }

Let d\phi  be the flux through the elemental area adx , then 

d\phi = Badx = \frac{\mu _0I(t)}{2\pi x}adx

Total flux through the square loop is 

\phi = \frac{\mu _0I(t)}{2\pi }a\int_{a}^{2a}\frac{dx}{x}

\phi = \frac{\mu _0I(t)a}{2\pi } log 2

= \frac{\mu _0I_o \cos wta}{2\pi } log 2

Now induced emf , 

            \varepsilon = \frac{-d\phi }{dt}=\frac{\mu 0}{2 \pi }a I_0w log 2 \sin wt

Power dissipated in loop is , 

p = \frac{\varepsilon ^2}{R}

p = \frac{\mu _{0}^{2}}{4\pi ^2}a^2I_{0}^{2}w^2\sin ^2 wt (log 2)^2\times \frac{1}{R}

 

 

 

 

 

 

Posted by

vinayak

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