Michael Faraday → studying relationship between electricity and magnetism.
Faraday discovered → that when he moved a magnet in and out of a coil → it induced a deflection on the galvanometer connected to the coil when the magnet was moved away from the coil → galvanometer deflected in the opposite direction. if the magnet was stationary → no deflection was recorded.
- he concluded that a changing magnetic field produces an induced current.
- this effect is known as electromagnetic induction.
Definition
Electromagnetic Induction is the process through which an induced e.m.f. is produced in a conductor due to a changing magnetic field. #PhysicsDefinitions
Law
Faraday’s Law of Electromagnetic Induction states that the magnitude of the induced e.m.f. in a circuit is directly proportional to the rate of change of magnetic flux in the circuit. Magnetic Flux is the magnetic field in a given area #PhysicsDefinitions
Law
Lenz’s Law states that the direction of the induced e.m.f. and hence the induced current in a closed circuit, is always such that its magnetic field effect opposes the motion or change producing it. #PhysicsDefinitions
According to Faraday’s law → an unchanging magnetic field → will not induce any current.
- this is why the galvanometer does not deflect → when magnet is inside the coil
- this is also why deflection is observed whenever the magnet is moved → regardless of the direction of movement → it also states that the faster the magnet is moved in and out of the solenoid → the greater the induced e.m.f is.
Lenz’s law → is a consequence of the law of conservation of energy. Energy
- total amount of energy in the universe must remain constant.
→ if magnetic field associated with current moves in same direction as the change in magnetic field that created it → these 2 magnetic fields would combine to create net magnetic field that would induce a current with twice the magnitude.
- energy would have been created.
- this would violate the law of conservation of energy.
- therefore → small amount of work is done when magnet is pushed into or pulled out of the coil
Magnitude of induced e.m.f increases if:
- speed of relative motion between the coil and the magnet is increased.
- number of turns of the coil is increased
- strength of the magnet is increased
When magnet is dropped through thick copper tube → current is induced in the copper tube and a magnetic field is generated by the induced current. this induced current produces magnetic field → that opposes the direction of the falling magnet → causing it to slow down.
Impossible to overstate the significance of Faraday’s discovery. Electromagnet induction → makes generators and transformers possible. It is the fundamentals of production and transmission of electricity.
Important
xxxxx creates a changing magnetic flux that cuts the coil