. What is Electromagnetic Induction
In 1831, Michal Faraday independently demonstrated an important experiment whereby he was able to establish that if the magnetic flux associated with a closed conducting loop is made to continuously change, an electric current is ‘induced’ in the loop (even though it does not have a voltage source attached). This induced current will be observed as long as the magnetic flux is ‘changing’ but will cease if the flux becomes constant. This remarkable phenomenon is called Electro-Magnetic Induction (EMI).
In the two possible schematic diagrams for such an experiment shown above, in (a) if the bar magnet is moved closer to the coil continuously a reading is observed in the galvanometer G. Also if the bar magnet is now moved continuously away from the coil, there again appears a reading, however the direction of the induced current observed reverses.
In setup (b), if the current through the coil in the circuit below is continuously varied using the variable resistance (Rheostat) shown, a reading is observed in the galvanometer G in the circuit above indicating an induced current. Again the direction of the induced current will change if the current in the lower circuit is made to increase as opposed to decrease.