Faraday's Law electromagnetic induction interactive demonstration showing how rate of flux change affects induced voltage
Stillness generates nothing
A powerful magnet sitting perfectly still inside a coil produces zero voltage, no matter how strong the field. Only when flux is changing does current flow. Set how fast the magnet moves in and out of the coil and watch the induced voltage.
Magnetic flux simulationMagnet parked
Change the magnet speed or the coil turns. Watch the emf.
Induced emf now: 0.0 mV
Magnet velocity
stationaryslowmoderaterapid
Coil turns
Peak dΦ/dt per turn
0.00 mWb/s
Peak emf ε (N = 50)
0.0 mV
Increasing the number of turns N in a coil proportionally increases the induced emf for the same rate of flux change. If you double the turns, you double the voltage. This is because each loop experiences the same rate of flux change, and the individual emfs add in series. Try it: switch the coil from 50 to 100 turns and Peak emf doubles, while Peak dΦ/dt per turn stays the same. Generators exploit this by using coils with hundreds or thousands of turns to maximise output from a given rotation speed. The formula ε = -NdΦ/dt shows this linear relationship explicitly.
Know This
The induced emf exists only while the flux is changing; a stationary magnet inside a coil produces zero emf regardless of field strength.