Transcript electricity - FreeScienceStuff.com

PS-6.6
Explain the relationships among voltage,
resistance, and current in Ohm’s law.
Key Concepts:
Voltage: volt
Resistance: ohm
Current: amp
Ohms law
Voltage
Voltage occurs because of difference in charge
between two points. This is electric potential
energy. The symbol for voltage is “V”.
Voltage is sometimes referred to as electrical
force. Voltage is the force like quantity that
can move electrical charge from one point to
another.
Voltage is created by a chemical cell when it changes chemical
energy to electrical energy
The acid electrolyte reacts with the Zinc metal releasing
electrons.
When a wire connects the terminals of a
battery then the voltage will push and pull
electrons through a conductor.
Electrons in the wire are pushed by the negative terminal
and pulled by the positive terminal through the wire.
A generator changes mechanical energy
to electric energy.
When a wire connects the terminals of a
generator then the voltage will push and pull
electrons through a conductor.
In all devices that
terminal has extra
charge. The other
electrons and thus
produce electrical current, one
electrons, thus a negative
terminal has a deficit of
a positive charge.
Electric current:
…is the flow of electrons through a conductor
is measured in amperes sometimes referred to as
“amps”. The symbol is (A).
1 ampere of electrical current is equal to
6.25 x 1018 ( a coulomb) electrons moving through
a circuit in one second!
REALITY CHECK: If you had 1 coulomb of sand grains you
would need all these dump trucks to hold them!
Resistance:
…happens when the electrons flowing through the
wire continually run into things ( in this case copper
atoms) in the wire and bounce around.
…Resistance opposes the flow electrons through a
conductor. The electrical resistance is like electrical
friction… it produces heat!
ELECTRICAL RESISTANCE:
…will slow the flow of current because it is
harder for the current to get through the
conductor.
Wires that have a larger diameter have less
resistance.
Longer wires have greater resistance.
Electric devices provide much of the
resistance in a circuit
Ohms law describes the relationship between
voltage, current, and resistance.
The voltage is the product of the current
and resistance. (V = I R)
One volt will pull one amp of current through
one ohm of resistance.
*** EXAMPLE:
What is the current in a 12V circuit
with a resistance of 200 Ohms?
I=V/R
I= 12V / 200 Ohms
I= .06A
Note: The letter I represents electrical current in Amperes in
the equation.
If the voltage increases and the
resistance remains the same the
current will increase.
If the voltage stays the same and
the resistance increases then the
current will decrease.
The End….
For Now.…