# (a) Define the term ‘self inductance’ of a coil. Write its S.I. unit.(b)  A rectangular loop of sides a and b carrying current is kept at a distance ‘a’ from an infinitely long straight wire carrying  current  as shown in the figure. Obtain an expression for the resultant force acting on the loop.

Self-inductance (L) is the emf induced in the coil when the rate of change of current in the coil is  ampere/second

Where = magnetic flux

= Current flowing

Where = coefficient of self- inductance or self-inductance of the coil

when,

Then,

The S.I unit of self-inductance is Henry (H).

(b) We know the magnetic field due to the infinitely long current-carrying wire is given by :

Where,

= current carried by infinite wire

= perpendicular distance of wire to that point.

Now, the force acting on a straight wire is given by,

For side  AB

in -ve x-direction.

Such that, for BC and AD forces are equal but opposite in direction so, they will cancel out each other.

Now, for side CD

in +ve x- direction

Hence, the net force will be in -ve x-direction ,

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