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Electric Current
Chapter 7-2
Electric Circuit
A closed
path through which
electrons can flow
Electrons flow because of a
difference in potential
When a switch is turned on it
causes electron to flow
Flowing Electrons
Remember
that static electricity is
the build up of electrons
When the static charge causes a
spark the flow of electrons that is
created is very short
Not long enough to run a light or a
computer
The
electrons always flow from
where there are more electrons
(higher potential) to fewer
electrons (lower potential)
Static discharge quickly
balances out the electrons and
there is no more difference in
potential
Current, I
The
flow of electrons
The amount of current depends
upon the number of electrons
passing every second
Measured in Amperes, Amps, A
Measured with an ammeter
Ampere
One
ampere is one coulomb of
charge passing every second
One coulomb is 6.24 billion
billion electrons
Potential Difference (Voltage)
The
difference in potential (the energy of
the electrons) between two different
places
Measured in volts (V)
Sometimes called voltage
Measured with a voltmeter
Doesn’t depend upon the number of
electrons only the energy the electrons
carry
Batteries
Current
must maintain a
difference in potential or the
current will stop
Batteries is a device that
maintains that difference in
potential
Batteries
supply the energy to keep
the electrons moving, they don’t
supply the electrons
Dry
cells-a positive electrode, a
negative electrode, and a moist
paste to pass the electrons
Wet cells-a positive plate, a
negative plate, and a liquid
solution to pass the electrons
Resistance, R
The
opposition to the flow of
electrons
Measured in Ohms, W
Copper is an excellent
conductor because it has low
resistance
Good & Bad Resistance
Toasters,
lights
Wiring
hair dryers, Christmas
Ohm’s Law
Determines
a relationship
between voltage, current
and resistance
If
the resistance increases
the current decreases
A greater voltage in a
circuit causes the current
to increase
George Simon Ohm
German
physicist found
experimentally
The
current in a metal
conductor is directly
proportional to the
potential difference across
it and inversely
proportional to the
resistance, Ohm’s Law
V = IR