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Review
• Just like Electricity, magnets work in FIELDS.
• Fields are drawn with VECTORS
• Review:Up, Down, Left and Right
Review
• With 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?
Magnetism
• Magnetism works in a field, like Electricity.
• We use B for the magnetic field variable.
Magnetism
• Magnets 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.
+ + + + + + + + +
- - -- - -- - -
Magnetism
• The left side is positively charged, right side negatively charged and the field would look like this:
+ + + + + + + + +
- - -- - -- - -
Magnetism
• If this were a magnet, there would be a North and South pole instead. Field looks the SAME
+ + + + + + + + +
- - -- - -- - -
N S
E & M
• Whenever you have an ELECTRIC CURRENT, there is a MAGNETIC FIELD too, and vice versa.
• One is always quite larger than the other.
E & M
• Ever had a power cord to close to a TV screen?
• The distortion is from the Magnet Field around the cord.
E & M
• Other Examples:• High Voltage Power lines
Big V Small B• MRI Machine
Huge V Medium B• Refrigerator Magnet
Medium B Tiny V
Magnetic Fields
• How do we know what the Magnetic Field looks like around a wire with current in it?
Magnetic Fields
• There are some rules to help us.
• They are called Right Hand Rules.
Step 1: USE YOUR RIGHT HAND!!
Right Hand Rule #1
• What does a magnetic field, B, look like around a wire?
• Grab some wire with your RIGHT hand
I
Right Hand Rule #1
• Your 4 fingers are lined up with the magnetic field. It goes in a circle around the wire.
I
Right Hand Rule #1
• A field diagram would look like this:(Remember the vector arrows)
Front Top Bottom
I
II I
Right Hand Rule #2
• What happens if we play with an electric cord in a magnetic field that was already there?
Right Hand Rule #2• So what happens when the power is turned
on? The wire starts moving! But what direction??
N (+)
S (-)
B
I
Right Hand Rule #2• Right Hand Rule #2 tells us in what direction
the wire will be pushed…
N (+)
S (-)
B
I
Right Hand Rule #2• Stick your thumb out. That’s the direction of
the force (the way the wire will go).
N (+)
S (-)
B
I