• Clara Chung
In summary, the conversation discusses the concept of induced voltage and current in a moving rod within a magnetic field. The participants analyze the direction and magnitude of the induced voltage and current and discuss how it relates to the motion of the rod and the overall circuit. They also consider the effects of the resistance and path of the circuit on the induced current.
Clara Chung

## The Attempt at a Solution

Yes. When the rod moves down, it moves across the horizontal field, cutting field lines. A current will be induced to oppose the motion. The magnetic force due to the motion is vertically upward.

But I think that, the voltage is induced in a direction perpendicular to the axis along PQ. No current can be formed. Therefore the rod will slide down as normal.

Why am I wrong? Thanks again.

Label the bottom two corners A and B ... A is below P and B is below Q.
By your reasoning, could there be a voltage induced between A and P?

If there were a voltage induced between P and Q, wouldn't the same voltage also be between A and B ... after all, these are conductors?

Clara Chung
Simon Bridge said:
Label the bottom two corners A and B ... A is below P and B is below Q.
By your reasoning, could there be a voltage induced between A and P?

If there were a voltage induced between P and Q, wouldn't the same voltage also be between A and B ... after all, these are conductors?

Yes, a voltage can be induced between A and P. However the same voltage is induced between B and Q. The situation will be just like a circuit with two batteries oppose to each other. Shouldn't there be no current?

Simon Bridge said:
If there were a voltage induced between P and Q, wouldn't the same voltage also be between A and B ... after all, these are conductors?
I'm so sorry that I don't get your point, do you mean the situation in ci)?

When the magnetic field is vertical - you have no problem with there being a current along the rod between P and Q right?
Does that mean there is a voltage induced between P and Q?

Clara Chung
Simon Bridge said:
When the magnetic field is vertical - you have no problem with there being a current along the rod between P and Q right?
Does that mean there is a voltage induced between P and Q?
yes it does.

OK then - in that situation, would there be the same voltage between A and B?

Sorry for asking stupid question. I think I now have problem with there being a current along the rod between P and Q. When a voltage is applied on PQ. That means PQAB is a short circuit. How do I account for the p.d. between AB?
By the way, there won't be induced emf on AB because it is not cutting any field lines.

Clara Chung said:
By the way, there won't be induced emf on AB because it is not cutting any field lines.
Correct.
Clara Chung said:
How do I account for the p.d. between AB?
That will depend on the resistances of the rod and the overall path, which are not given. The motional emf in the rod will be B*l*v, which will drive a current through the loop PQAB and ∫along loop PQABE.dl=dΦ/dt= B*l*v.

Clara Chung
cnh1995 said:
Correct.

That will depend on the resistances of the rod and the overall path, which are not given. The motional emf in the rod will be B*l*v, which will drive a current through the loop PQAB and ∫along loop PQABE.dl=dΦ/dt= B*l*v.

Thanks and please take a look at the questions on #1 and #3.

Clara Chung said:
But I think that, the voltage is induced in a direction perpendicular to the axis along PQ. No current can be formed. Therefore the rod will slide down as normal.
No. Apply the right hand rule and you'll see that an emf is induced in the rod along its length and it is equal to Blvsinθ, where θ is the angle between velocity vector and the magnetic field direction.
Clara Chung said:
Yes, a voltage can be induced between A and P. However the same voltage is induced between B and Q. The situation will be just like a circuit with two batteries oppose to each other. Shouldn't there be no current?
This would be true if the entire loop PQAB were moving. In this problem, since only the rod PQ is moving, motional emf is induced only in the rod, which circulates a current in the loop.

Clara Chung

## 1. What is magnetic induction?

Magnetic induction is the process by which a magnetic field is created in a material when it is exposed to an external magnetic field. This can occur through the movement of electrons or changes in the magnetic field.

## 2. How does magnetic induction work?

Magnetic induction works through the principles of electromagnetism. When a material is exposed to an external magnetic field, the magnetic field induces a current in the material, creating its own magnetic field. The interaction between the two fields results in a change in the magnetic properties of the material.

## 3. What are some real-life applications of magnetic induction?

Magnetic induction has many practical applications, such as in generators, transformers, and electric motors. It is also used in wireless charging, magnetic levitation, and magnetic resonance imaging (MRI).

## 4. How is magnetic induction related to Faraday's law?

Magnetic induction is closely related to Faraday's law of induction, which states that a changing magnetic field will induce an electromotive force (EMF) in a conductor. This is the basis for many applications of magnetic induction in technology and everyday life.

## 5. What factors affect the strength of magnetic induction?

The strength of magnetic induction depends on several factors, including the strength of the external magnetic field, the distance between the material and the source of the field, the material's magnetic permeability, and the electrical conductivity of the material.

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