- #1
Dorian Black
- 12
- 0
Hi,
Imagine a conductive wire bent to the shape of a loop without its ends meeting. A magnet is moved with respect to the loop such that the magnetic field crossing it (perpendicularly) is linearly increasing with time (Φ=kt) where k is a constant. The induced emf is the rate of change of magnetic flux; this being a constant (k). But then the emf across an inductor is Ldi/dt. So the current in the loop must be rising linearly with time. This current will consequently place opposite charges at both ends of the wire and build up a potential difference there. This potential should keep on growing as long as the magnetic flux carries on rising linearly in the loop. But here's the problem:
∫E⋅dL (closed path)=-N x dΦ/dt (Faraday's Law)
The left side gives a value that rises continuously with time (voltage across the two ends), while the left doesn't do so (dΦ/dt = k).
Grateful to anyone who points out where I got this fatally wrong.
Many thanks.
Imagine a conductive wire bent to the shape of a loop without its ends meeting. A magnet is moved with respect to the loop such that the magnetic field crossing it (perpendicularly) is linearly increasing with time (Φ=kt) where k is a constant. The induced emf is the rate of change of magnetic flux; this being a constant (k). But then the emf across an inductor is Ldi/dt. So the current in the loop must be rising linearly with time. This current will consequently place opposite charges at both ends of the wire and build up a potential difference there. This potential should keep on growing as long as the magnetic flux carries on rising linearly in the loop. But here's the problem:
∫E⋅dL (closed path)=-N x dΦ/dt (Faraday's Law)
The left side gives a value that rises continuously with time (voltage across the two ends), while the left doesn't do so (dΦ/dt = k).
Grateful to anyone who points out where I got this fatally wrong.
Many thanks.