Download File - Physical Science

Physical Science Goal 4
Electricity and Magnetism
Static Electricity
• Static Electricity—electricity that is not
moving.
• Basic Law of Electrostatics
– Like charges repel, opposite charges attract!!
• How do objects become “charged”????
– Objects become charged by gaining or losing
electrons!! Protons will not move!!!
3 ways to charge an object:
1. Conduction—direct contact
•
No contact, no conduction
2. Friction—Rubbing together
3. Induction—Rearrangement of charge of a
neutral object caused by a nearby charged
object!
Current Electricity
• Voltage will determine whether electricity will
or will not flow!!!!
• Resistance determines how much current
flows!!
– Low resistance, high current
– High resistance, low current
Electricity Symbols and Units
Quantity
Symbol in Equation
Unit
Symbol Unit
Current
I
Amperes
A
Resistance R
Ohms
Voltage
V
Volts
W
V
Power
P
Watts
W
Electricity Equations
2 Types of Electric Circuits:
Series Circuit
Parallel Circuit
• Current has only one path
to take.
• All of the current will travel
through each device.
• “Cheap” Christmas tree
lights.
• Current has more than one
path to take.
• All of the current will not
travel through each device.
• “Expensive” Christmas tree
lights.
Series Circuit:
In a series circuit, if one
of the lights goes out,
what happens to the
remaining light(s)?
Hence, the
“Cheap
lights”!
Parallel Circuit
In a parallel circuit,
if one light goes
out, what happens
to the remaining
lights?
Hence, the
“Expensive lights!!
Discuss Current through each of the
lightbulbs in the pictures below:
Magnetism
• Like Poles repel, opposite Poles attract!!
Lines of Repulsion
Lines of Attraction
• Magnetic Field Lines always move out of the
north pole and into the south pole!!!
• Magnets are strongest at the poles!!
• If you break a bar magnet in half, you get 2 bar
magnets both with a north and a south pole!!
Magnetic Domains
• In a permanent magnet, the “Domains” are aligned. In
a normal piece of metal, the domains are not aligned!!
• You can only make a magnet from Iron, cobalt and
Nickel(Iron Triad)
Electromagnetism
• Oersted—If a current moves through a wire,
there will be a magnetic field produced
around the wire.
• Faraday—If you move a wire through a
magnetic field, or a magnetic field through a
wire, there will be a current induced in the
wire!!
Electromagnet
• A temporary magnet. Will quit working when
the current is turned off.
• 3 requirements:
1. Iron Core
2. Turns of Wire(conductor)
3. Current
2 ways to strengthen Electromagnet:
1. Increase the current
2. Increase the # of turns of wire
Motor vs. Generator
•
Motor—converts electrical energy into
mechanical energy(something turns)
• Generator—converts mechanical energy into
electrical energy(you get electricity)