Lenz's law - magnetic fields and Currents

In summary: So, the current in B will be equal to the current in A.In summary, the conversation discusses Lenz's law and the relationship between the current and the change in flux through a loop when the magnetic field is changing. The direction of the magnetic field and the change in flux play a crucial role in determining the magnitude of the current in each situation. In situation A, where the magnetic field is increasing, the current is at its highest. In situation B, where the magnetic field is both increasing and decreasing, the current is equal to that in situation A due to the change in flux through each half of the loop pointing in the same direction. In situation C, where the magnetic field is decreasing, the current decreases until it becomes constant
  • #1
kidi3
26
0
Hey Pf..

I am trying to understand Lenz's law, but somehow it doesn't make sense.
In my book there is some checkpoints execise to test wheather you've understood what you read about, one those checkpoints looks like this.

http://snag.gy/NCNLh.jpg


I do understand why the current in situation a is the highest since the magnetic field is increasing will it never become zero, and in situation C will the current decrease until become constant (B=0)=> current =0.
But why should the current in situation B be as high as in situation A.. ?
 
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  • #2
kidi3 said:
But why should the current in situation B be as high as in situation A.. ?
Take note of the direction of the magnetic field in each half of the loop.
 
  • #3
It's both in and out.. but wouldn't the dec. part go to 0, and lead the B to become ½A..
I can see B would be as high as A in a short moment,should it not be ½A thereby lead B<A
 
  • #4
kidi3 said:
It's both in and out.. but wouldn't the dec. part go to 0, and lead the B to become ½A..
No.

What matters is the change in the flux through each half of the loop.

In the top half (of B) which way does the field point? Since it's increasing, which way is the change in flux pointing?

Same question for the bottom half. Which way does the field point? Since it's decreasing, which way is the change in flux pointing?
 
  • #5
Ah.. they all point in the same direction, and since change is equal to the one in situation A, they must be equal in magnitude..
 
  • #6
kidi3 said:
Ah.. they all point in the same direction, and since change is equal to the one in situation A, they must be equal in magnitude..
Exactly. The change in flux through each half of B points in the same direction, just like it does in A.
 

Related to Lenz's law - magnetic fields and Currents

1. What is Lenz's law and what does it state?

Lenz's law is a fundamental law of electromagnetism that describes the direction of induced current in a conductor when it is exposed to a changing magnetic field. It states that the direction of the induced current is always such that it opposes the change that produced it.

2. How does Lenz's law relate to Faraday's law of induction?

Lenz's law is a consequence of Faraday's law of induction, which states that a changing magnetic field will induce an electromotive force (EMF) in a closed circuit. Lenz's law specifies the direction of the induced EMF and current.

3. Can Lenz's law be used to predict the direction of induced current?

Yes, Lenz's law can be used to predict the direction of induced current in a conductor. It states that the induced current will always flow in a direction that opposes the change in magnetic field.

4. How does Lenz's law apply to electric motors and generators?

Lenz's law is crucial in the operation of electric motors and generators. In an electric motor, the direction of the induced current in the rotor opposes the change in the magnetic field produced by the stator, causing the rotor to rotate. In a generator, the rotation of the rotor causes a change in the magnetic field, which induces a current that flows in the opposite direction, producing electricity.

5. Can Lenz's law be violated?

No, Lenz's law is a fundamental law of electromagnetism and has been experimentally verified to hold true in all cases. It is a consequence of the law of conservation of energy and cannot be violated.

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