Please help me! (1 Viewer)

[kutmasterking]

Hi,

I was wondering if anybody could be so kind to provide me with a bit of an explanation for the following syllabus outcomes, since i suck at physics.. gggg

topic 2:
- account for Lenz's law in terms of conservation of energy & relate it to the production of back emf in motors
- explain that, in electric motors, back emf opposes the supply emf
- explain the production of eddy currents in terms of Lenz's law

topic 4:
- explain why voltage transformations are related to the conservation of energy.

oohhhh any help would be greatly appreciated!
please please pleaseeee

thanks!

 

[Forbidden.]

Hi,

I was wondering if anybody could be so kind to provide me with a bit of an explanation for the following syllabus outcomes, since i suck at physics.. gggg

topic 2:
- account for Lenz's law in terms of conservation of energy & relate it to the production of back emf in motors
- explain that, in electric motors, back emf opposes the supply emf
- explain the production of eddy currents in terms of Lenz's law

topic 4:
- explain why voltage transformations are related to the conservation of energy.

oohhhh any help would be greatly appreciated!
please please pleaseeee

thanks!

Pushing a magnet through a closed coil and it pushes back at you
(It does define Lenz's Law & Law of Energy Conservation obeyed)
Why? The energy you give into pushing that magnet gets converted into energy in a form that pushes the magnet back at you.

Pushing a magnet through a closed coil and it accelerates.
(It does NOT define Lenz's Law NOT obeyed & Law of Energy Conservation NOT obeyed)
Why? The energy came from nowhere. You put in some energy to push the magnet and energy came from nowhere to give the magnet an increase in velocity.

Energy can only be changed in one form or another, not destroyed or created.
Lenz's law obey's this ? Yes.

In a motor, applied emf from a battery for example, the rotor will rotate through a magnetic field.
If it's slow, there won't be much back emf.
The coil rotates through the magnetic field slowly and will be repelled in the form of back emf.
If it's spinning very fast, there will be lots of back emf.
The greater the velocity of the rotor, the more back emf's going to oppose the supply emf.




Transformers do obey the law of energy conservation.
Let's say in an IDEAL transformer, the power input is 2400W.
The power output is also 2400W.
What you put in is what you get.

The power output can never be over 2400W and greater than the power input.
Otherwise, energy has been created from nowhere !
So transformers like everything else, also obey the law of energy conservation.


(In a real transformer the power output is a little bit less.)
(In all cases, Power Input > Power Output)

 

[kutmasterking]

Heeeey thanks so much!