Download Ch 17 Introduction to electricity

CH 17 INTRODUCTION TO ELECTRICITY
https://youtu.be/EJeAuQ7pkpc
I. ELECTRICAL CHARGE AND STATIC ELECTRICITY
A. ELECTRIC CHARGE
1. All matter is composed of atoms
2. Atoms have 1protons, 2electrons, & 3neutrons
•
Protons (+)
•
Electrons (-)
•
Neutrons (neutral or no charge)
3. Charged objects exert a force
•
Push or pull
4. Law of electrical charges= like charges repel (push away) &
opposite charges attract
5. Protons (+) and electrons (-) attract each other or the atom
would not stay together
6. Electrical force= force of attraction or repulsion on a charged
particle that is die to an electric field
•
Depends on:
1 Amount
of charge on each object (greater the charge=
greater the force)
2
Distance between the charges (closer together= greater
the force )
7. Electrical field= the space around a charged object in which
an electric force is exerted on another charged object
•
Other object will either be attracted or repelled
STOP AND THINK……
• What are 2 types of charged particles in an atom?
• Postive (+) Protons
• Negative (-) Electrons
B. CHARGE IT!
1. An object becomes POSITIVELY charged when it
LOSES electrons
• Losing negatives makes it more positive
2. An object becomes NEGATIVELY charged when it
GAINS electrons
• Gaining negatives makes it more negative
3. Three ways to charge an
object:
a. Friction= electrons are
“wiped” from one object to
another- rubbing a balloon
on your head)
b. Contact (Conduction)=
electrons move from one
object to another by touch
https://youtu.be/T0J5q43MSw8
c. Induction= charges in an
uncharged metal object
are rearranged without
direct contact with a
charged object
C. CONSERVATION OF CHARGES
1. Charges are not created or destroyed when you charge
something by any of the 3 methods
2. The numbers of electrons & protons stay the same
3. Electrons are simply transferred from one object to the next
D. DETECTING CHARGES
1. Electroscope= device that
detects charges
2. Metal strips will hang straight
when it is not charged
3. If a charged object touches
the electroscope the strips
will repel (move apart)
4. Does NOT show if the
charged object is positive or
negative
LAB: CREATING AN ELECTROSCOPE TO DETECT
CHARGES
•
https://youtu.be/-JsVZwc1dOo
E. STATIC ELECTRICITY
1. “Static“ = not moving
• Charges of the static electricity do not move away from the
object they are in
2. Static electricity = the electric charge at rest on an object
3. Examples: static cling & charged balloons
• Friction transfers the charge to the clothes or balloon and
since the objects are insulators the charge stays after the
friction ceases
3. Electric Discharge: the loss of electricity as charges move off
an object
https://youtu.be/yc2-363MIQs
a. When you touch a door knob after shuffling your feet
b. Lightening is caused by the large charge difference &
rapid electrical discharge
4. Lightening rods on top of buildings are grounded so the
charge goes into the Earth be absorbed
• Lightening strike the highest point
F. MOVING CHARGES
1. Electrical conductors=
materials in which charges can
move easily
• Most metals
2. Electrical insulators=
materials in which charges
cannot move through easily
• Electrons are held very
tightly in these materials
• Plastic, rubber, glass, wood
& air
3. Semiconductors: special
class of materials that
conduct electric charge
better than electrical
insulators, but not as good
as electrical conductors
• Silicon used in computer
chips
G. ELECTRIC CURRENT
1. Electric current = rate at which charges pass a given point
a. Higher the current the greater the number of charges that
pass the point each second
b. Unit of measurement for electric current is expressed in
amperes (amps)
c. Amps symbol A
d. Symbol for current in formulas = I
2. Charges in the current are transferred from electron to electron
3. The electric field that causes the electrons in the wire to move
•
Electrons are slow but since the current turns them all on at
once the work simultaneously
4. Two kinds of electric current: https://youtu.be/xyQfrzBfnDU
a. DC direct current= charges always flow in the same
direction
•
Used in batteries
b. AC alternating current= charges shift from flowing in one
direction to flowing in the reverse direction
•
Electric in outlets
•
https://youtu.be/fNpIq0gOTAk Edison vs Tesla