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Moving Charges And Magnetism

Question
CBSEENPH12039842

Two similar coils of radius R are lying concentrically with their planes at right angles to each other. The currents flowing in them are I and 2I, respectively. The resultant magnetic field induction at the centre will be

  • fraction numerator square root of 5 straight mu subscript straight o straight I over denominator 2 straight R end fraction
  • fraction numerator 3 straight mu subscript straight o straight I over denominator 2 straight R end fraction
  • fraction numerator straight mu subscript straight o straight I over denominator 2 straight R end fraction
  • fraction numerator straight mu subscript straight o straight I over denominator straight R end fraction

Solution

A.

fraction numerator square root of 5 straight mu subscript straight o straight I over denominator 2 straight R end fraction

The magnetic field (B) at the centre of circular current carrying coil of radius R and current I,
straight B equals space fraction numerator straight mu subscript straight o straight I over denominator 2 straight R end fraction
Similarly comma space if space current space equals space 2 straight I comma space then
Magnetic space field space equals space fraction numerator straight mu subscript straight o 2 straight I over denominator 2 straight R end fraction space equals space 2 straight B
so space resultant space magnetic space field
equals space square root of straight B squared space plus left parenthesis 2 straight B right parenthesis squared end root space equals space square root of 5 straight B squared end root space
square root of 5 straight B end root

space equals space fraction numerator square root of 5 straight mu subscript straight o straight I over denominator 2 straight R end fraction