The expression for the induced e.m.f. contains a negative sign `[e=-(dphi)/(dt)]`. What is the significance of the negative sign?

The expression for the induced emf contains a negative sign (xi=-(dphi)/(dt)) . The significance of the negative sign is given by the statement

What is induced e.m.f.?

For a wave propagating in the positive x direction the instantaneous displacement of the particle is y=A sin ""(2pi)/T (t-x/v) . What is the significance of the negative sign ? If positive sign is used, what does it represent?

The total energy of the electron in an hydrogen atom is En = -13.6/n^2 eV What is the significance of the negative sign?

Show that the total energy of an electron in an atom is negative and it is E=-e^2/(8piepsilon_0) . What is the significance of the negative energy.

Why is osmotic potential given a negative sign?

Define Poisson's ratio.Write an expression for it. What is the significance of negative sign in this expression ?