# Permanent magnet with residual magnetization and Induced EMF

Let's consider a permanent magnet and a coil. No current flows through the coil. Can the permanent magnet induce an EMF into the coil (and thus an induced current)? Why? Many thanks.

• Hint: A changing magnetic field induces an electric field.
– sbp
Nov 17 '17 at 20:22
• @sbp Yes, for sure. But why can a magnet with remanent magnetization considered as a changing magnetic field? Magnetization is a property of a 'magnetized' ferromagnetic material related to the magnetic field measured inside the material... what could I misunderstand? Thanks! Nov 17 '17 at 21:08
• Okay. It's not about a ferromagnetic material having a changing magnetic field. The field is constant for such a material. Say I fix the loop. Now I bring in the magnet from far away. So for the loop there was initially no $B$, but as I bring the magnet closer there is a changing $B$ that the loop feels, there is a change in flux, and thus current flows in the loop. Infact the current flows in such a direction so as the abhor this change in $B$. This is called Lenzs Law. Look up Griffiths.
– sbp
Nov 18 '17 at 3:35
• @sbp Ok, if some movements are allowed, everything is clear. But in a device like this one physics.stackexchange.com/questions/369212/…, where permanent magnet and coil are attatched, I have to conclude that the current induced by the permanent magnet was induced at the beginning of the assembly process.. Is it correct? Thanks again! Nov 21 '17 at 16:59
• See the point is that $\textbf{B}$ should change with time to induce $\textbf{E}$ and viceversa.
– sbp
Nov 21 '17 at 20:01