- 96 Views
- Uploaded on
- Presentation posted in: General

Magnetism

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

- Electrons produce electric fields.
- Moving electrons produce magnetic fields.
- Electron spin produces the major portion of an objects magnetic field.
- MOST elements have electrons with opposite spins, which cancel each other.

- SOME elements, like iron and nickel, have an unbalanced number of electrons spinning in one direction and produce magnets.
- A bar magnet produces a magnetic field with a north and south pole.
- If you break it in half, the new magnets have north and south poles.

- Magnetite is naturally magnetic and remains magnetic forever.
- Most iron and ceramic magnets are placed in contact with a true magnet to be magnetized. They don’t last forever.
- Dropping or heating them can weaken fields by realigning electrons.

- Magnets may also be created by passing electric current through wires or coils of wires. These are called electromagnetics.
- As current passes through a straight wire, a magnetic field is created in concentric circles surrounding the wire.
- In a coil of wire, the field more closely resembles a doughnut shape.

- If an electric charge moves through a magnetic field at a given velocity, it experiences a force that is perpendicular to the plane of the field and the velocity vector.
- This requires a basic understanding of the cross product.

- Calculate the magnitude and direction of the force created when an electron moves at a velocity of 5 x 1017 m/s to the right through a magnetic field of strength 5000 Tesla directed into the white board.

- A magnet moved in and out of a coil of wire produces electricity.
- This is called inducing a current, or induction.
- The greater the number of coils, the higher the induced current.
- When a magnet moves into a coil, it produce a different current than when it moves out of a coil. This is AC current.

- Faraday’s law states that the induced voltage in a coil is proportional to the product of the number of loops, the cross sectional area of the loops, and the rate at which the magnetic field changes within those loops.

- Electric motors use electrical energy to create magnetic fields which allow the motor to turn.
- Motors use electricity to create motion. Generators work in the opposite direction: they turn mechanical energy into electricity.
- A generator uses an energy source (windmill, hydroelectric plant, steam turbine, etc) to turn a wire loop in a magnetic field which in turn produces electricity.

- Transformers are used to increase or decrease the voltage.
- For example, at the power generating plant, a step-up transformer is used to increase or step up the voltage for transmission down the power lines.

V1/V2 = n1/n2 is used to calculate the number of coils required on each side to step up or down a current.

- Calculate the number of coils on the secondary side needed to step 14,400 volts down to 120 volts if there are 5000 coils on the primary side.
- Calculate the voltage produced on the secondary side if 200 volts are provided to the primary side, which has 1500 coils and a secondary coil count of 14500.