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. Drag the slider to control how fast the magnet moves through the coil and watch the induced voltage spike.
Magnetic flux simulationMoving at 0 m/s
Magnet velocity controls rate of flux change
Induced emf: 0.00 V
Magnet velocity
stationaryslowmoderaterapid
Rate of change dΦ/dt
0.00
Induced emf ε
0.00 V
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. A 100-turn coil moving through a field at the same speed as a 10-turn coil generates ten times the voltage. 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.