The expression for the induced e.m.f contains a negative sign $\left[e=-\frac{d\varphi }{dt}\right]$.

What is the significance of negative sign?

Given expression of induced emf,

$\left[e=-\frac{d\varphi }{dt}\right]$

It determines an electromotive force E that only takes the forces brought about by the charge of the electrons into account.

Here,

$\varphi =$magnetic flux

t=time

Here, negative sign is used as emf opposes the change in the magnetic flux.