Two coaxial solenoids 1 and 2 of the same length are set so that one is inside the other. The number of turns per unit length are n1 and n2. The currents i1 and i2 are flowing in opposite directions. The magnetic field inside the inner coil is zero. This is possible when
i1≠i2 and n1=n2
i1=i2 and n1≠n2
i1=i2 and n1=n2
i1n1=i2n2
As we learnt in
Magnetic field due to Infinite length solenoid -
Bin=
- wherein
Point is well inside the solenoid
For
Option 1)
i1≠i2 and n1=n2
incorrect
Option 2)
i1=i2 and n1≠n2
incorrect
Option 3)
i1=i2 and n1=n2
correct
Option 4)
i1n1=i2n2
incorrect