Download Electricity and Magnetism

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
Brought to you by
Barr/Batten
Does
your clock radio wake you in the
morning?
The source of electrical energy lies in
the forces between electric charges in
atoms
Electric
Charges
o Positive (Proton)
o Negative (Electron)
o Neutral (Neutron)
o Atoms are neutral so # of protons and
electrons are equal
 Forces
between charges
o Like charges repel
o Opposite charges attract
o Charge decreases with distance
o Objects do not have to be touching for electric
charges to exert force

Making objects electrically charged
o Charging by contact
• Atoms need to touch– rubbing balloon on your hair, clothes in the dryer
o Charging by induction
• No electric charge transfer, just movement of the charges– after you
rub the balloon you can stick it to the wall

Conductors and Insulators
o Conductors– hold electrons loosely allow them to flow easily
o Insulators- hold electrons tightly do not allow them to flow easily

Static Charge
• Imbalance of electric charge on an object
o Electric Discharge
• Movement of static charge from one object to another– spark when you
touch the doorknob
o Lightning
• Example of static discharge
o Lightning Safety
• On average lightning strikes about 400 people in the US
• If the time between lightning and thunder is less than 30 sec, seek
shelter for 30 min until after the last flash
o Grounding
• The process of providing a path to drain excess charge into Earth –
lightning rods

What is it?
o Flow of electric charge

Unit for Current?
o SI unit is the ampere, the symbol is A
o 1 ampere means an enormous number of electrons– like a billion
billion– flowing into and out of the wire every second

Simple Electric circuit
o The closed path which electric charges can flow through

Voltage
o Measure of the amount of electrical energy transferred by an electric
charge
o Ohm’s Law– the relationship between voltage, current and resistance in
a circuit
• Voltage(in volts)= current (in amperes) x resistance (in ohms)
• V=IR

Series circuit
o Devices connected so there is only on path

Parallel circuit
o Devices connected so there is more than one
path for the current to follow

Magnets
o Magnetic Poles
• Two ends of a magnet– one is North and one is South
o Forces between poles
• Magnetic poles exert force on other magnets—like repel, opposites
attract
o Magnetic Fields
• Magnetic force that surrounds the magnet

Magnetic Materials
o Only metals that contain, iron, cobalt,
& nickel

Electromagnetism
o Electricity and magnetism are different, but related
o A current carrying wire wrapped around an iron core
o Strength is dependent on the current flowing in the wire

Generating Electric Current
if a magnet is moved through a wire loop
o Or is a wire loop is moved in a magnet
o Current can be generated
o