# Electromagnetic Induction - Faraday's/Lenz's Law

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Thread starter 6 years ago
#1
I'm confused about the minus sign in the equation; emf = -N (change in)Magnetic Flux/(change in)time

The book says; The minus sign in the equation above shows that... The induced emf could send an induced current around the circuit that would set up a magnetic field that would oppose the change in magnetic flux that is causing the induced emf. This is called Lenz's law and is really an example of the law of conservation of energy.

I don't get how the induced current was produced?
And how does that produce a magnetic field?
That oppose the change in magnetic flux that caused the induced emf?
how is that an example of the conservation of energy?

Sorry, i just really don't understand and i'm trying my best to
0
6 years ago
#2
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0
6 years ago
#3
(Original post by pureandmodest)
I'm confused about the minus sign in the equation; emf = -N (change in)Magnetic Flux/(change in)time

The book says; The minus sign in the equation above shows that... The induced emf could send an induced current around the circuit that would set up a magnetic field that would oppose the change in magnetic flux that is causing the induced emf. This is called Lenz's law and is really an example of the law of conservation of energy.

I don't get how the induced current was produced?
And how does that produce a magnetic field?
That oppose the change in magnetic flux that caused the induced emf?
how is that an example of the conservation of energy?

Sorry, i just really don't understand and i'm trying my best to
You need to understand well the right hand grip tile, see this
http://www.electricyouniverse.com/ey...and-rules3.jpg

Then see this
http://www.ksh
(all of this is one site, the link is messed up if i write it all on one line)

Myself, I thinking I'm understanding it more with that. I might give an explanation to you later on, not now though.
0
6 years ago
#4
It's just about making some sense for me
1
Thread starter 6 years ago
#5
(Original post by krisshP)
http://www.k****ij-school.com/Study-...z’s-law.aspx

See that. Myself, I thinking I'm understanding it more with that. I might give an explanation to you later on, not now though.

The link doesn't work
0
6 years ago
#6
(Original post by pureandmodest)
The link doesn't work
I edited the post.
0
6 years ago
#7
Sorry about the annoying ads that pop up twice there, but the site is actually quite good in explaining it.
0
6 years ago
#8
(Original post by pureandmodest)
T

Remember field lines are like force lines representing force.

Imagine if we didn't have Lenz's and that the induced current produces a magnetic field in an opposite direction as to the one shown on that site. Then there'd be an attractive force exerted on the magnet towards the conductor rather than a repulsive force, making accelerate towards the conductor. As the magnetic gets even closer to the conductor due to this acceleration, there's a flux linkage change (there's more field lines per unit area perpendicularly passing through the conductor). Hence on the conductor there's an induced emf and so a current. This current produces a magnetic field as usual (a current produces a magnetic field around it, and a magnetic field, in the form of a magnetic flux linkage change, produces a current. If you are given one, you can work out the direction of the other using the right hand grip rule). Without Lenz's law, the direction of the magnetic field arising from this current would NOT oppose the flux linkage change (right) that formed it, so it "adds" to it. Hence there's an even bigger force on the magnet, making it accelerate further more. But overall, without Lenz's law, you get increasing force out of nowhere, and so increasing acceleration out of nowhere. Therefore you get increasing kinetic energy put of nowhere, going against principle of conservation of energy.

There MAY be a flaw there, I'm new to Lenz's law as well and have recently found it very painful to understand as well .
0
Thread starter 6 years ago
#9
(Original post by krisshP)
Remember field lines are like force lines representing force.

Imagine if we didn't have Lenz's and that the induced current produces a magnetic field in an opposite direction as to the one shown on that site. Then there'd be an attractive force exerted on the magnet towards the conductor rather than a repulsive force, making accelerate towards the conductor. As the magnetic gets even closer to the conductor due to this acceleration, there's a flux linkage change (there's more field lines per unit area perpendicularly passing through the conductor). Hence on the conductor there's an induced emf and so a current. This current produces a magnetic field as usual (a current produces a magnetic field around it, and a magnetic field, in the form of a magnetic flux linkage change, produces a current. If you are given one, you can work out the direction of the other using the right hand grip rule). Without Lenz's law, the direction of the magnetic field arising from this current would NOT oppose the flux linkage change (right) that formed it, so it "adds" to it. Hence there's an even bigger force on the magnet, making it accelerate further more. But overall, without Lenz's law, you get increasing force out of nowhere, and so increasing acceleration out of nowhere. Therefore you get increasing kinetic energy put of nowhere, going against principle of conservation of energy.

There MAY be a flaw there, I'm new to Lenz's law as well and have recently found it very painful to understand as well .

It's just that, i'm trying really hard to just understand the concepts when i'm reading the textbook but i'm finding it so hard to even do that.
I just can't get my head wrapped around it :| and then someone says something and i get even more confused and i just don't know :c
0
6 years ago
#10
(Original post by pureandmodest)
It's just that, i'm trying really hard to just understand the concepts when i'm reading the textbook but i'm finding it so hard to even do that.
I just can't get my head wrapped around it :| and then someone says something and i get even more confused and i just don't know :c
Are you okay with Faraday's law and confused on Lenz's law? If yes, just forget your textbook for Lenz's law and just try the advice and link I posted above, it may "click" for you. Even my textbook didn't make sense for me, but I'm starting to now feel okay with it
0
6 years ago
#11
The emf can be produced by many variables, the sun, by movement or motion, water or electric current or by a stationary bicycle with a belt or chain or traditional bicycle depending on how the device is mounted & what it is being used for. I didn't include nuclear because that is much too dangerous& volitale
with emf. It is still using energy be it negative or positive. The negative sign is because of the change in magnetic charge
0
6 years ago
#12
Magnetic charge?
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