We know that photon has no charge. Then where from it gets electric and magnetic field in light?
Malik Sajad asks
Electric and magnetic fields are not produced by the photon; it is massless too.
But, photon is created by time varying electric and magnetic fields, usually produced by accelerated charges.
As you might have already learnt, a charge at rest produces an electric field around it. A moving charge (current) produces a magnetic field around it as well as magnetic field. A varying current produces a varying magnetic field and hence an induce emf or current. An accelerated charge produces a time varying electric and magnetic fields.
Thus under suitable situations, the electric and magnetic fields can reinforce each other and propagate out as pure electromagnetic form of energy and such a packet of energy is called photon.
How can an alternating current change its direction while moving in a wire or any conductor? Why direct currents aren’t used in Home circuits?
Alternating current is produced by rotating a coil in a strong magnetic field (or by rotating magnet around the coil)
So, during every half rotation the direction of emf (voltage) induced in the coil reverses and hence the current too reverses its direction. The frequency of ac in India is 50 Hz and therefore in every 1 sec there will be 100 changes in direction.
Alternating currents are suitable for long distance as it can be stepped up using transformer to minimize energy loss and can be stepped down for use at home.