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JEE Mains · Physics · STD 12 - 4. Moving charges and magnetism
One of the two small circular coils, (none of them having any self- inductance) is suspended with a \(V-\) shaped copper wire, with plane horizontal. The other coil is placed just below the first one with plane horizontal. Both the coils are connected in series with a \(dc\) supply. The coils are found to attract each other with a force. Which one of the following statements is incorrect ?
- A Both the coils carry currents in the same direction
- B Coils will attract each other, even if the supply is an ac source
- C Force is proportional to \(d^{-1}\)
- D Force is proportional to \(d^{-2}\)
Answer & Solution
Correct Answer
(D) Force is proportional to \(d^{-2}\)
Step-by-step Solution
Detailed explanation
As the force between the two coils is attractive hence currents in the coil must be in the same direction and the force, \(F \propto \frac{{{I_1}{I_2}}}{{2\pi d}}\) where \(I_1\) and \(I_2\) are the currents flowing through the coils.
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