Two coaxial solenoids having same number of turns per unit length n, and radius R and `2R` respectively have no current initially. Current in both grows uniformly such that current in the inner one is twice that of the outer one, at any instant of time in the same direction. Current in outer one at time `t` is `Kt` then induced electric field at a distance r from axis is `(R lt r lt 2R)`.

The magnetic field on the axis of a long solenoid having n turns per unit length and carrying a current is

The current flowing in two coaxial coils in the same direction. On increasing the distance the two, the electric current will

The current flowing in two coaxial coils in the same direction. On increasing the distance the two, the electric current will

A long solenoid of radius 2R contains another coaxial solenoid of radius R . The coils have the same number of turns per unit length and initially both carry zero current. At time, t=0 , current start increasing linearly with time in both solenoids. At any moment the current flowing in the inner coil is twice as large as that in the outer one and their directions are same. A charged particle, initially at rest between the two solenoids, start moving along a circular trajectory due to increasing current in the solenoid as shown in the figure What is the radius of the circle ? (Assume magnetic field due to each solenoid remains uniform over its cross-section.)

A long solenoid has a radius a and number of turns per unit length is n . If it carries a current i, then the magnetic field on its axis is directly proportional to

A long solenoid has a radius a and number of turns per unit length is n . If it carries a current i, then the magnetic field on its axis is directly proportional to