07-May-2010, 10:12 AM
(This post was last modified: 18-May-2010, 04:17 AM by Ajita Kamal.)
so lemme begin how i teach Back Emf in motors:
In electrical engg we cannot show current however we can show the effects of current, the stuff that you require is: some students, about 1 meter long insulated copper wire, two paper clips,magnet and a digital power supply(showing current and voltage)
to make the simplest motor in the world just make a few windings on a battery(AA size), about 20 of them wud be enough and then take out two ends on the either side of the wire... now scrap of the insulation from one side completely and half from the other side(otherwise it will not work), bend the paper clips so that they form a support to our motor, now put the entire apparatus on a bread board and give supply to the paper clip and make sure the magnet is in between the two paper clips.
Now block the motor and you will find a high current reading in the power supply as you leave the motor to rotate the current drops to almost to 40% of its initial value.. so something might have opposed the applied voltage thereby decreasing the potential difference and that is the BACK EMF which is the emf produced ny the rotating motor....i will you a link which is very helpful... do not get afraid with the american specification the local counter parts easily
http://sci-toys.com/scitoys/scitoys/elec...ectro.html
In electrical engg we cannot show current however we can show the effects of current, the stuff that you require is: some students, about 1 meter long insulated copper wire, two paper clips,magnet and a digital power supply(showing current and voltage)
to make the simplest motor in the world just make a few windings on a battery(AA size), about 20 of them wud be enough and then take out two ends on the either side of the wire... now scrap of the insulation from one side completely and half from the other side(otherwise it will not work), bend the paper clips so that they form a support to our motor, now put the entire apparatus on a bread board and give supply to the paper clip and make sure the magnet is in between the two paper clips.
Now block the motor and you will find a high current reading in the power supply as you leave the motor to rotate the current drops to almost to 40% of its initial value.. so something might have opposed the applied voltage thereby decreasing the potential difference and that is the BACK EMF which is the emf produced ny the rotating motor....i will you a link which is very helpful... do not get afraid with the american specification the local counter parts easily
http://sci-toys.com/scitoys/scitoys/elec...ectro.html