JEE Advanced2018PhysicsMagnetic Effects of CurrentActual
Two infinitely long straight wires lie in the xy - plane along the lines x = ± R . The wire located at x = + R carries a constant current I 1 and the wire located at x = - R carries a constant current I 2 . A circular loop of radius R is suspended with its centre at 0 , 0 3 R and in a plane parallel to the xy - plane. This loop carries a constant current I in the clockwise direction as seen from above the loop.
Options
- AIf I 1 = I 2 , t h e n B → cannot be equal to zero at the origin 0 , 0 , 0
- BIf I 1 > 0 a n d I 2 < 0 , t h e n B → can be equal to zero at the origin 0 , 0 , 0
- CIf I 1 < 0 a n d I 2 > 0 , t h e n B → can be equal to zero at the origin 0 , 0 , 0
- DIf I 1 = I 2 , Then the z-component of the magnetic field at the centre of the loop is ((- 0 I / 2 R ) )
Correct answer
A. If I 1 = I 2 , t h e n B → cannot be equal to zero at the origin 0 , 0 , 0
Step-by-step solution
( A ) At origin, B → = 0 due to two wires if I 1 = I 2 , h e n c e B → n e t at origin is equal to B → due to ring, which is non-zero. ( B ) If I 1 > 0 a n d I 2 0 , B → at origin due to wires will be along + k ^ direction and B → due to ring is along - k ^ direction and hence B → can be zero at origin ( C ) If I 1 0 a n d I 2 > 0 , B → at origin due to wires is along - k ^ and also along - k ^ due to ring, hence B → cannot be zero ( D )