Faraday's Law — Definition
Definition
Imagine you have a coil of wire and a magnet. If you hold the magnet still near the coil, nothing much happens electrically. But what if you move the magnet? If you push the magnet towards the coil, or pull it away, something remarkable occurs: an electric current starts flowing in the coil, even though there's no battery connected!
This phenomenon, where a changing magnetic field produces an electric current, is called Electromagnetic Induction. Faraday's Law is the rule that tells us *how much* electricity is produced and *how* it's related to the magnet's movement.
At the heart of Faraday's Law is a concept called 'magnetic flux.' Think of magnetic flux as the total number of magnetic field lines passing through a certain area. If you have a strong magnet, it has many field lines.
If you place a coil in this field, some of these lines will pass through the loop of the coil. The more lines passing through, the greater the magnetic flux. Faraday discovered that it's not the presence of a magnetic field itself that creates current, but rather the *change* in this magnetic flux.
If the number of magnetic field lines passing through the coil changes over time, an electromotive force (EMF) is induced. This EMF is essentially the 'voltage' that drives the induced current.
So, if you move the magnet faster, the magnetic flux changes more rapidly, and Faraday's Law tells us that a larger EMF will be induced, leading to a stronger current. If you stop moving the magnet, the flux stops changing, and the induced current disappears.
The law also states that if you have more turns in your coil, the induced EMF will be proportionally larger because each turn contributes to the total EMF. The direction of this induced current is given by another related law, Lenz's Law, which essentially says the induced current will always try to oppose the change that caused it.
For example, if you push a North pole towards a coil, the induced current will create a North pole on the coil's face to repel the incoming magnet, thus opposing the motion. This simple yet profound law underpins much of our modern electrical technology.