When a current changes from +2A to –2A in 0.05s, an emf of 8V induced in a coil. The coefficient of self induction of coil is 
 

Given data: An emf of 8V is created in a coil when the current switches from +2A to -2A in  0.05 seconds.

Concept used: current electricity.

Detailed solution:

Current electricity is the electricity produced by the movement of electrons. Static electricity is the electricity that accumulates on a substance surface.

$$\begin{gathered} \varphi =\text{li} \\ \Rightarrow \frac{\text{d}\varphi }{\text{d}1}=\frac{\text{Ldi}}{\text{d}1} \\ 8=\text{L}\left(\frac{4\times 100}{0.05}\right) \\ \text{L}=\frac{8}{80}=0.1\text{H } \end{gathered}$$