Which of the following best states the meaning of the negative sign in the expression E=−dtdΦ?
a) It shows that the induced emf acts so as to oppose the magnetic field producing the flux.
b) It shows that the induced emf acts so as to oppose the change in magnetic flux.
c) It only indicates that the magnitude of the induced emf equals the rate of change of magnetic flux.
d) It means that the induced emf is always negative in value.