Electric motors & faraday's law

[jackd]

Homework Statement

Eliza connects a power supply, switch, and a multimeter (in ammeter mode) in series with a wire coil. The wire coil is held into place by 2 connecting wire leads. One of the wire leads has been stripped off of the insulating enamel coating so that half the wire is bare; the other lead has been completely stripped bare.

1. What orientations of the coil will give a current through it due to the battery?

2. During the time that there is a current through the coil, which side of the coil will act like a north pole and which side will act like a south pole? Explain?

3. How will the coil behave when placed above the magnet and the switch is closed?

Homework Equations

Faraday's Law: E=-d(magnetic flux)/dt
Magnetic Flux = B*Acos($$\theta$$

The Attempt at a Solution

The part without coating will give a current, but the part that has coating will not?
Very lost...

 

[Redbelly98]

The part without coating will give a current, but the part that has coating will not?

Yes.

For the rest, it's hard to see what's going on without a figure.

 

[baba89]

I would like to clarify and expand on the information provided in the homework statement. Firstly, the setup described in the statement is known as a simple electric motor, where a wire coil is placed in a magnetic field and a current is passed through it to create motion. The power supply, switch, and multimeter are used to control and measure the current flowing through the coil.

1. The orientation of the coil that will produce a current depends on the direction of the magnetic field and the direction of the current. According to Faraday's law, when a conductor (such as the wire coil) moves through a magnetic field, a current is induced in the conductor. This current is directly proportional to the rate of change of the magnetic flux, as given by the equation E=-d(magnetic flux)/dt. Therefore, the coil must be oriented in a way that allows it to move through the magnetic field in order for a current to be induced.

2. When a current flows through the coil, the coil itself becomes an electromagnet. The direction of the magnetic field produced by the coil depends on the direction of the current flowing through it. Using the right-hand rule, we can determine that the side of the coil with the bare wire lead will act as the south pole and the side with the fully stripped lead will act as the north pole. This is because the direction of the current is clockwise when looking at the coil from the bottom, and the magnetic field lines produced by a current-carrying wire follow the right-hand rule.

3. When the coil is placed above a magnet and the switch is closed, the coil will experience a force due to the interaction between the magnetic fields of the coil and the magnet. This force will cause the coil to rotate, as the current flowing through the coil creates a magnetic field that interacts with the magnetic field of the permanent magnet. The direction of rotation can be determined using the right-hand rule, where the thumb points in the direction of the current and the fingers curl in the direction of the force.

In summary, the orientation of the coil, the direction of the current, and the interaction between the coil's magnetic field and the external magnetic field are all important factors in understanding the behavior of an electric motor. Faraday's law is a fundamental principle that explains the relationship between magnetic fields and electric currents, and is essential for understanding the operation of electric motors.