MagnetsAnd Magnetic Fields
ReviewJust like Electricity, magnets work in FIELDS.
Fields are drawn with VECTORS
Review:Up, Down, Left and Right
ReviewWith Magnetism, we will need to look at vectors in 3-D.
How do we draw a vector arrow going into the page?
What would a real arrow look like going away from us?
ReviewKind of like this:
So we draw it like this:
ReviewWhat would a real arrow look like coming directly toward you?
So we draw it like this:
MagnetismMagnetism works in a field, like Electricity.We use B for the magnetic field variable.
MagnetismMagnets work a lot like a PROTON and an ELECTRON.
Imagine a bar of metal with all the PROTONS on one end and the ELECTRONS on the other.+ + + + + + + + + - - - - - -MagnetismThe left side is positively charged, right side negatively charged and the field would look like this:+ + + + + + + + + - - - - - -MagnetismIf this were a magnet, there would be a North and South pole instead. Field looks the SAME+ + + + + + + + + - - - - - -NSElectricity and MagnetismElectricity and Magnetism are chained together.
E & MWhenever you have an ELECTRIC CURRENT, there is a MAGNETIC FIELD too, and vice versa.One is always quite larger than the other.
E & MEver had a power cord to close to a TV screen?
The distortion is from the Magnet Field around the cord.
E & MExample: Current vs. Magnetic Field in a power cord
LARGE currentSMALL magnetic field
E & MOther Examples:High Voltage Power linesBig VSmall BMRI MachineHuge VMedium BRefrigerator MagnetMedium BTiny V
Magnetic FieldsHow do we know what the Magnetic Field looks like around a wire with current in it?
Magnetic FieldsThere are some rules to help us.
They are called Right Hand Rules.
Step 1: USE YOUR RIGHT HAND!!
Right Hand Rule #1What does a magnetic field, B, look like around a wire?
Grab some wire with your RIGHT hand
IRight Hand Rule #1Make sure your thumb is going in the same direction as the current is!I
Right Hand Rule #1Your 4 fingers are lined up with the magnetic field. It goes in a circle around the wire.I
Right Hand Rule #1A field diagram would look like this:(Remember the vector arrows)Front Top BottomI
IIIRight Hand Rule #2What happens if we play with an electric cord in a magnetic field that was already there?
Right Hand Rule #2Well set it up like this:IN (+)S (-)Right Hand Rule #2Even without the wire, the magnets have a field already:N (+)S (-)BRight Hand Rule #2So what happens when the power is turned on? The wire starts moving! But what direction??N (+)S (-)BIRight Hand Rule #2Right Hand Rule #2 tells us in what direction the wire will be pushed N (+)S (-)BIRight Hand Rule #2STEP 1: USE RIGHT HAND!!!N (+)S (-)BIRight Hand Rule #2Index Finger points with B.N (+)S (-)BIRight Hand Rule #2Other three point with IN (+)S (-)BIRight Hand Rule #2Stick your thumb out. Thats the direction of the force (the way the wire will go).N (+)S (-)BIPracticeThe 2nd Right Hand rule will take some getting used to:#1- Index finger with B
#2- Other three with I
3#- Thumb gives you the answer