And also, could someone please explain how a coloured TV works? Like is it basically the same as a cathode ray tube only with three electron guns? :O Sorry for the bombardment of questions, have trials in two days ;;
From memory the answer to this question is yes. One electron gun for each of the three digital colours. Each gun makes one of the three metals in one pixel glow blue/red/green.
Hey! Just a question about back EMF - i'm a little confused as to how it is caused, what it actually is, and how it affects the motor. Would be awesome if someone could give an explanation. Cheers!
So a bit of background information:
We know that by Faraday's law, if an electrical conductor is subject to a change in magnetic flux, some EMF is induced.
We also know that by Lenz's law, the induced EMF always seeks to oppose the cause of induction.
But here's the thing. As a consequence of Faraday's law, it doesn't matter whether we move the conductor or the magnetic field. If the magnetic field is moved then obviously an EMF will be induced. However, if a conductor is moved through a magnetic field, that also triggers electromagnetic induction.
So keep in mind that for your motor, the armature (coils) are basically conductors moving through a magnetic field! This is the EMF induced into the motor.
Applying Lenz's law, the cause of induction is the current forcing the coils to rotate in the magnetic field. The reason why it's "back" EMF is that well, by Lenz's law it's going to try to make the coils go back the other way.
What does this do? There will be a point where this EMF induced cannot oppose the actual voltage of the circuit anymore. So this effectively puts a limiting (maximum) velocity on what a motor can achieve.