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Two long parallel wire separated by a distance R have equal current I flowing in each. The magnetic field of one exerts a force F on the other. The distance R is increased to 2 R and the current in each wire is reduced from I to I / 2. what is the force between them now ?

Option: 1

\mathrm{4 F}


Option: 2

\mathrm{F}


Option: 3

\mathrm{F / 4}


Option: 4

\mathrm{F / 8}


Answers (1)

best_answer

The force per unit length is
\mathrm{F=\frac{\mu_0}{4 \pi} \times \frac{2 I^2}{R} }
If R is increased to 2 R and I is reduced to I / 2, the force per unit length becomes

\mathrm{F^{\prime} =\frac{\mu_0}{4 \pi} \times \frac{2(I / 2)^2}{2 R} \\ }
\mathrm{ =\frac{\mu_0}{4 \pi} \times \frac{2 I^2}{R} \cdot \frac{1}{8}=\frac{F}{8} }

 

Posted by

Anam Khan

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