- 58 Views
- Uploaded on

Download Presentation
## PowerPoint Slideshow about 'Phy 103: Fundamentals of Physics' - pembroke

**An Image/Link below is provided (as is) to download presentation**

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 - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript

Magnetic Poles

N S

- Since magnetism is created by moving charge, there is no single source of magnetism (such as a single electron)
- All magnets have both
- a north pole
- a south pole
- Magnetic poles are never

occur themselves

- Aside from the obvious geographic reference, the south and north poles are magnet equivalent to positive and negative charge

Magnetism & Magnetic Force

N

N

S

S

S

N

N

S

- The magnetic poles interact similarly to electric charge
- “like” poles repel
- “unlike” poles attract

Magnetic Fields

S

B

N

- The movement of electric charge produces a magnetic field (a B field)
- Magnets have magnetic fields associated with them
- Magnetic fields are essentially the magnetic influence a magnet has on the space around it
- Magnetic field lines always point from North to South
- The field lines originate at the North pole
- The field lines terminate at the South pole
- The units of magnetic field are called Tesla (T)

1 Tesla (T) = 1 N.s/C.m

Electric Currents & Magnetic Fields

- Wires carrying electric current produce magnetic fields
- The magnitude of the magnetic field is related to:
- Current in wire (I)
- Distance from wire (r)

B ~ I/r

- To calculate the B field:
- The magnetic field “curls” around the wire!!

Andre Marie Ampere (1775-1836)

- First person to describe current as the flow of electricity along a wire
- Published his derivation of the electrodynamic (electric) force law in 1826

- Considered to be the “Newton of electricity”
- Not formally educated (well did not attend school)
- Reputed to have mastered all known mathematics by the age of 12 (probably untrue)
- Worked on an electrical & magnetic wave theory of light

Electromagnets

- A coil of wire with current running through is an electromagnet
- The magnetic field inside the coil is constant and points long the length of the coil
- The strength of the electromagnet depends on:
- The current (I)
- The number of coils (N)
- The length of the coil (L)

Bcoil ~ I.N/L

Magnetic Force (on charged particles)

- When an electric charge (such as an electron) moves through an magnetic field, it experiences a magnetic force
- The magnitude of the magnetic force depends on:
- The charge (q)
- The velocity of the charge (v)
- The magnetic field (B)

Fmagnetic = q.v.B

- The direction of the magnetic force is perpendicular to both:
- The direction of the field
- The direction of motion (v)

Magnetic Force(on current carrying wires)

- When two current carrying wires are aligned parallel to each other they exert a magnetic force on each other
- Each wire is in the magnetic field of the other
- The direction of the force depends on the relative direction of the electric currents in te wires:

I1

I1

F

F

Repulsive:

Attractive:

F

F

I2

I2

Earth’s Magnetic Field

- The Earth has a magnetic field and acts like a giant big magnet
- We define the magnetic “north” direction as the direction the North end of a compass points
- The geographic “North Pole” is really the South pole of the magnetic field
- The geographic “South Pole” is really the North pole of the magnetic field
- Although its value varies depending on location, the magnitude of the Earth’s magnetic field (Bearth) is

Bearth ~ 60 x 10-6 T

Download Presentation

Connecting to Server..