SAC 3 - created from Mind Map

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Magnets

Motors

Transformers

Filled with Dipoles

Soft or hard

Cannot seperate a N and S pole

Magnetic field

Flux

Dipoles randomly arranged

Dipoles arranged in one line

No magnetic effect

Magnetic effect

Soft easy to de/magnetise

Hard hard to de/magnetise

Region where a magnetic material experiences a force

Forces Diagram

https://upload.wikimedia.org/wikipedia/commons/thumb/0/0c/VFPt_cylindrical_magnet_thumb.svg/250px-VFPt_cylindrical_magnet_thumb.svg.png

Field lines travel from N to S

Earth's Magnetic Field

http://www.epa.gov/esd/cmb/GeophysicsWebsite/pages/reference/_img/NewImages/Magnetic%20Susceptability/earth-magfield.jpg

What we call the North Pole is actually the earth's South Pole. Due to this north magnets are attracted to it.

Vector

Magnetic fields are always apparent when current flows

Field is stronger closer

On diagrams..

x goes into the page

. goes out of the page

Think of a feathered arrow. Cross at the back going away from you.

Field Strength (B)

Force on an electron in a field

F= BvQ, where v = velocity and Q = charge (charge = 1.6E^-19 for electrons)

E.g. compass

Force Formula

F=nBIL

Where N = Number of wires, B = Field strength (Tesla), I = Current (amperes) and L = Length of wire in field (m)

This works when perpendicular when not, F=nBILsin(theta). Where theta is the angle between current and field.

If Current and Field is parallel, F=0

Field Diagram and Right Hand Grip Rule

http://courses.ae.utexas.edu/ase463q/design_pages/fall02/wavelet/3_sour8.gif

Parallel Wires

http://www.physchem.co.za/OB11-ele/graphics/magnetic1_f8.gif

Right Hand Solenoid Rule

http://etc.usf.edu/clipart/35600/35671/rhrsole_35671_md.gif

Solenoid Field Diagram

http://www.met.reading.ac.uk/pplato2/h-flap/phys4_4f_4.png

When current flows field strength equals

B = (kI)/r

Where k is a constant, I is current and r is radius.

If current and field are parallel, F=0

Right Hand Slap Rule

http://www.ph.unimelb.edu.au/~mkl/640162/prot/module1/image/RHruleI.gif

Tesla (T)

Typically...

Permanent magnets typically are B = 10^-3 to 1T

The Earth's field is B ~ 5x10^-5T

The amount of magnetic field in a region

Wb = B x A

Where B = Field strength (T) and A = area (m^2)

Amount of turns is irrelevant

If field and coil parallel, = 0

EMF

Size and density

Area not diameter!

Convert dimensions to m before calculating area

Voltage

Created by batteries, generators etc.

Formula

-A*(Change in Flux/Change in time) OR -B*(Change in Area/Change in time)

DC

http://electrical4u.com/electrical/wp-content/uploads/2013/03/dc-motor-parts.jpg

Generators

RHS can be applied

Motor requires split ring commutator

http://fcw2.needham.k12.ma.us/~michael_h/Physics/FOV1-00112C20/FOV1-00112C2C/S045D68FC.0/1713_105349_0.png

To increase turning force increase n, B, I or L or use a wider motor.

Results in Torque

Commutator repeatedly changes direction of current and force

DC (Dynamo)

"DC Motor in reverse"

You spin, it produces voltage/current

RMS

Only work on AC

Changes number of turns on unput compared to output

Power in = Power out

E.g. If Voltage increases, current decreases (As P=VI)

Done in Ratios

N1/N2 = V1/V2 = I2/I1 Where N = Turns

AC RMS is equivalent of DC not RMS; should be equal

Amplifies/diminishes voltage