Q22 of 26 Page 1

(i) Define self-inductance. Write its SI units.

(ii) A long solenoid with 15 turns per cm has a small loop of area 2.0 cm2 placed inside the solenoid normal to its axis. If the current carried by the solenoid changes steadily from 2.0 A to 4.0 A in 0.1 s, what is the induced emf in the loop while the current is changing?


The magnetic flux associated with the coil when the unit current flows through it is known as self-inductance. The unit of self-inductance is Henry and it is symbolically represented by H. One henry is defined as the emf induced when the rate of change of current in the coil is 1 ampere/second.


(ii) Given:


Number of turns per unit centimetre, n = 15 turns/cm=1500 turns/m


Area of the loop, A=2.0 cm2


Current, I1=2 A


Current, I2=4 A


Time, t = 0.1 s


Calculation:


Magnetic field associated with initial current,



Magnetic field associated with final current,



Change in flux is given by,



Induced EMF is given by,



This is the induced EMF when current is changing.


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