Electric Current
Chapter 23
Electric Current
• Electric Current can simply be called the flow
of electric charges.
• The rate of electric flow is called amperes
(amps).
• A current-carrying wire is not electrically
charged like in the statics lecture.
Voltage Sources
• Charges must be pushed or driven by electric
potential (voltage).
• In every day life we use generators and
chemical batteries.
• When a circuit is completed charges move,
but voltage stays the same.
Electrical Resistance
• How much current flows is dependant on
electrical resistance (W).
• Electrical resistance can be though of as how
easily charges can move through the material.
• In a wire resistance is based on thickness,
warmth, and material.
Ohm’s Law
• Ohm’s Law describes the simple relationship
between current, voltage, and resistance.
• Current = voltage/resistance
• By changing any one of these elements the
output can change drastically.
Ohm’s Law and Electric Shock
• When shocked it is not the Voltage that is
damaging, but the current.
• Electric shock requires an electric potential
(voltage).
• This is why birds on power lines do not get
shocked when on power lines.
AC/DC
• Direct Current (DC) is charges flowing in
one direction.
• DC is used in most electronic devices.
• Alternating Current (AC) was developed by
Nikola Tesla as a more efficient way of
transporting mass electricity.
AC/DC Continued
• With AC the current moves through a wave
pattern known as a sinusoid.
• In North America the voltage and current
alternate at 60 cycles per second.
• Voltage in North America is 120v. This is due
to the original light bulbs burning out at
higher voltages.
• AC can be converted to DC.
Speed and Source of Electrons
• A signal through a circuit is transmitted at
nearly the speed of light.
• Electrons in the circuit do not travel at the
speed of light, merely the electric field the
nudges them.
Electric Circuits
• Any path which electrons flow is called a
circuit.
• The two most basic circuit setups are Series
and Parallel.
Series Circuit
• With a series circuit all the elements are in a
line. When one breaks the current stops.
• All the elements “see” the same current.
• All the elements share the voltage drop.
• The total resistance of the circuit dictates how
much current is seen.
Parallel Circuit
• With a parallel circuit each element has a path
to the voltage source.
• If one element fails the others will continue to
function.
• All the elements have the same voltage.
• All the elements divide up and share the
current.
Referances
• http://scienceworld.wolfram.com/biography/
photo-credits.html