Electro magnetic Induction problem. Simple one, but check wehre I am wrong.

In summary, the conversation discusses a problem involving electromagnetic induction where a magnet moves down through a coil and exits below, with a request to plot the graph of the induced emf in the coil over time. The equation for emf is mentioned and it is noted that as the magnetic field B increases, the emf becomes more negative, but when leaving and B decreases, the emf becomes more positive. It is clarified that the emf is first negative and forms a V shape in the negative emf region, then an inverted V in the positive emf region when it leaves. The textbook answer is mentioned, stating that the emf is first positive. The person then asks where they went wrong and it is determined that the emf is
  • #1
chound
164
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Electro magnetic Induction problem. Simple one, but please check wehre I am wrong.

Homework Statement



A magnet moving down, goes through a coil and exits it below. Plot the graph showing variation of induced emf in coil with time.

Homework Equations



emf = - Flux/Time

The Attempt at a Solution


As the magnetic field B increases, emf becomes more and more negative.
Then while leaving, B decreases, emf becomes more and more positive.

Hence

The emf is first negative, forms a V shape in the negative emf region and then an inverted V in the positive emf region when it leaves.

4.Answer in the textbook
The emf is first positive ... in other words just the opposite of what I said.

Where did I go wrong ?
 
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  • #2
From what two points are you measuring the emf?
 
  • #3
From either ends of the coil
 
  • #4
Isn't the "B" in this system a vector?

(Those tricky vectors...)

:cool:

~A137
 
  • #5
Ya. But how will that matter?
 
  • #6
I think I get it now.
Initially B and Area vectors are antiparallel, so flux is negative. Hence, the induced emf is positive.
 

FAQ: Electro magnetic Induction problem. Simple one, but check wehre I am wrong.

1. What is electromagnetic induction?

Electromagnetic induction is the production of an electric current in a conductor when it is exposed to a changing magnetic field.

2. How does electromagnetic induction work?

Electromagnetic induction works by moving a conductor through a magnetic field or by changing the magnetic field around a conductor. This creates a flow of electrons, or electric current, in the conductor.

3. What are some real-world applications of electromagnetic induction?

Some common applications of electromagnetic induction include generators, transformers, electric motors, and induction cooktops.

4. What factors affect the strength of induced current in a conductor?

The strength of induced current in a conductor is affected by the strength of the magnetic field, the speed at which the conductor moves through the field, and the angle between the conductor and the direction of the magnetic field.

5. How is electromagnetic induction related to Faraday's law?

Faraday's law states that the magnitude of the induced electromotive force (EMF) in a closed circuit is directly proportional to the rate of change of the magnetic flux through the circuit. This law is the basis for understanding how electromagnetic induction works.

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