Huygen’s Principle states that each and every point on a wavefront serves as a source of wavelets which then spread forward at the same speed. The new wavefront is in a line tangent to all of the wavelets.
A transformer is basically an electric device intended to transfer electric power from one electric circuit to another, without changing its frequency. Most widely used are the transformers for transmitting electric energy to houses from power stations, while others may be used in electronic appliances for the purpose of regulating voltage. Voltage needs to be regulated because the electrical appliances’ requirement is different from that of the electric current supplied. Hence regulators are fitted along with appliances to control the supply of current to avoid any short circuiting.
Michael Faraday discovered electromagnetic induction in 1831 and published his results for the experiments.
For the experiment, he wrapped two wires around the opposite sides of an iron ring. He plugged one of the wires into a galvanometer and observed as he connected the other side of the wire to a battery. As expected (due to the discovered properties of electromagnets), he observed the wave of electricity (a transient current) to flow when he connected the wire to the battery and another one when he disconnected the wire to the battery. He explained the electromagnetic induction by using the concept of lines of force.