(a) Describe a simple experiment (or activity) to show that the polarity of emf induced in a coil is always such that it tends to produce a current which opposes the change of magnetic flux that produces it.
(b) The current flowing through an inductor of self inductance L is continuously increasing. Plot a graph showing the variation of
(i) Magnetic flux versus the current
(ii) Induced emf versus dI/Dt
(iii) Magnetic potential energy stored versus the current.

Explanation

(b) (i) `phi=LI`
`phi prop I`
Shape of graph is

(ii) As `epsilon=L(dI)/(dt)`
Therefore the shape of the graph is

(iii) Magnetic Potential Energy `U=(1)/(2)LI^(2)`
Therefore, the shape of the graph is