Draw a labelled diagram of a magnetic relay and explain it's working

Relay is a controlling device just like a switch. handling high current with smaller current is the function of the relay.

Explanation:

There is a coil with the iron core is used as an electromagnet to operate the contact switch. When the control switch is closed the magnet operates the contact closed by attracting the metal terminal of the contacts switch. then current will passed throw the contact switch to load. When the control switch is open, the magnetic force will release and open the contact switch.

In a lot of applications, these replays are used to operate to control high current. it can control both AC and DC, but the magnetic coil works only dc.

speed of light in vacuum is 300,000 km/s

speed of light in other mediums is given by the expression v = c/n, where c is the speed of light in vacuum and n is the refractive index of medium.

for the first medium v = 200,000 km/s

  so, refractive index of medium = 300000/200000 = 1.5

    1.5 refractive index is usually for glass. so first medium is glass.

for the second medium v = 250,00 km/s

so, refractive index of medium = 300000/250000 = 1.2

    1.2 refractive index is usually for water. so second medium is water.

for the third medium v = 0 km/s

so, refractive index of medium = 300000/0 = ∞

    ∞ refractive index is usually for opaque mediums. so third medium is opaque medium.