Download Electric Charge and Static Electricity

Electric Charge and Static Electricity
Matter is made up of small particles called atoms. Atoms are made up of
smaller, sub-atomic particles called protons, neutrons, and
electrons.
Sub-atomic particles have a basic property called electric charge.
protons - positive charge
neutrons - neutral, no charge
electrons - negative charge
Electric Charge and Static Electricity
Protons and Electrons determine charge
Atoms have equal numbers of protons (positive)
and electrons (negative) therefore, atoms are
neutral, with no charge.
An atom that loses electrons will have more
protons than electrons = positive charge.
An atom that gains electrons will have more
electrons than protons = negative charge.
Electric Charge and Static Electricity
Static electricity - the build up of electric charge due to
the electrons transferring from one object to another.
Electrons do not flow. Remain at rest = “static”.
Methods of Charging an Object
I. Friction - when an object is rubbed, it will gain or lose
electrons and will gain a positive or negative charge
glass rod rubbed with silk =glass rod loses electrons
plastic rod rubbed with fur = plastic rod gains
electrons
++ - - SILK
++- - +
Glass Rod
Balloon on a person’s hair???
Electric Charge and Static Electricity
Static electricity - the build up of electric charge due to
the electrons transferring from one object to another.
Electrons do not flow. Remain at rest = “static”.
Methods of Charging an Object
II. Conduction - electrons transferred by direct contact
electrons move from one object to another.
conductor—a material that allows the flow of electrons.
silver, copper, aluminum, mercury
insulator—a material that resists the flow of electrons.
rubber, glass, wood
Electric Charge and Static Electricity
Static electricity - the build up of electric charge due to
the electrons transferring from one object to another.
Electrons do not flow. Remain at rest = “static”.
Methods of Charging an Object
III. Induction - rearrangement of electrons caused by
charged object placed next to neutral object. charge is
“induced” when electrons move away, or attract.
No contact.
ELECTRIC CHARGE
• van de graaff
http://phet.colorado.edu/en/simulation/balloo
ns
http://phet.colorado.edu/en/simulation/travolt
age
Electric Charge and Static Electricity
Law of Charges- like charges repel, opposite charges
attract
Symbol for charge is “q”
Charge is measured in COULOMB’s
1 proton = 1.602 x 10-19 C
1 electron = -1.602 x 10-19C
Electric Charge and Static Electricity
Coulomb’s Law – describes the electric force between any
two charges, separated by a distance “r”
The force of electrical attraction between two charges is
directly proportional to the product of the two charges and
inversely proportional to the square of the distance between
them.
k = 8.9875 x 109 Nm2
C2
Many charges are expressed in micro-coulombs (C);
1 x 106 C = 1 C. Easiest solution, whenever you see C, just add x 10-6
C to the number.
Ex. 5 C = 5 x 10-6 C; 28 C = 28 x 10-6 C
Coulomb’s Law Example
• Two electrostatic point charges of 60 C and 50 C exert a
repulsive force on each other of 175 N. What is the distance
between the two charges?
• Q1 = 60 x 10-6 C; Q2 = 50 x 10-6 C.
F
k  Q1  Q2
d2
k  Q1  Q2
d 
F
2
F  d 2  k  Q1  Q2
d
N  m2
6
6
8.9875 x 10

60
x
10
C

50
x
10
C
2
C
175 N
9
d
k  Q1  Q2
F
d  0.3925 m
Electric Current
Electrical current is the flow of electrons. Unlike static electricity,
charges are in motion.
Two types of Current
I. Direct current (DC) - flow of electrons in one direction.
car battery, flashlight batteries, photovoltaic (solar) cell
II. Alternating current (AC) - flow of electrons back and forth along
a path.
electric generator
Electric Current
CURRENT (I) – flow of electrons along a conductor
unit: ampere (amp)
1 ampere = 1 coulomb/1sec
RESISTANCE ( R ) – opposition to the flow of electrons. Electrons do work
and lose energy in the form of heat.
unit: ohm (W)
Jsec/coulomb2
VOLTAGE ( V ) Potential Difference - energy available to move electrons
from objects of high potential to objects of low potential energy. measures
amount of work electrons can do if they move between two points.
unit: volt (V)
1 volt = 1Joule/1 coulomb
High voltage greater potential to do work.
Low voltage less potential to do work.
e'
e'
e'
High potential energy
charged
Low potential energy
uncharged
Electric Current
OHM‘S LAW - current is dependent on voltage and resistance.
It is directly proportional to voltage and inversely proportional to resistance.
current = voltage
resistance
I = V
R
units: amps = volts
ohms
The greater the voltage, the greater the current
The lower the voltage, the lower the current
The lower the resistance, the greater the current
The greater the resistance, the lower the current
Electric Circuits
Circuit – path, or loop, formed by a conductor that allows electrons to flow.
SERIES CIRCUIT - circuit where current travels through only one loop
PARALLEL CIRCUIT - circuit consisting of several smaller circuits
connected together
Electric Circuits
Circuit – path, or loop, formed by a conductor for electrons to flow.
SYMBOLS -
conductor
switch (open)
switch (closed)
power source
(battery)
flow
light bulb
resistor
Fuse - metal in a circuit which melts when current is too high
Circuit breaker - metal in a circuit which bends when current is too high