CIRCUITS
ELECTRON FLOW IN CIRCUITS
• In metals, electric current is a flow of
electrons.
• How fast do these electrons move?
• Electrons flow, at speeds on the order of
centimeters per minute in DC
circuits(battery). And in AC circuits the
electrons don't really flow at all, instead
they sit in place and vibrate.
•
"ELECTRICITY" MISCONCEPTIONS IN K-6 TEXTBOOKS - - -William J. Beaty
•
http://www.amasci.com/ele-edu.html
ELECTRON FLOW IN CIRCUITS
• If the electrons are moving so slowly, why
then does the light bulb turn on in such an
instantaneous manner when we flip the
switch?????
http://www.glenbrook.k12.il.us/gbssci/phys/Class/circuits/u9l4d.html
ELECTRON FLOW IN CIRCUITS
• It's the energy in the circuit which flows fast,
not the electrons.
• Metals are always full of movable electrons. In a
simple circuit, all of the wires are totally packed
full of electrons all the time. And when a battery
or generator pumps the electrons at one point in
the circuit, electrons in the entire loop of the
circuit are forced to flow, and energy spreads
almost instantly throughout the entire circuit.
This happens even though the electrons move
very slowly.
•
"ELECTRICITY" MISCONCEPTIONS IN K-6 TEXTBOOKS - - -William J. Beaty
•
http://www.amasci.com/ele-edu.html
BICYCLE TIRE DEMO
Circuit diagrams are a pictorial way of showing circuits. Electricians and
engineers draw circuit diagrams to help them design the actual circuits. Here is
an example circuit diagram.
This is the Ammeter symbol.
This is the Voltmeter symbol.
This is the resistor symbol.
This is the battery symbol
http://www.ndt-ed.org/EducationResources/HighSchool/Electricity/circuitdiagrams.htm
SERIES AND PARALLEL
CIRCUITS
• Series and parallel electrical circuits are two
basic ways of wiring components. The naming
describes the method of attaching components
• A series circuit is one that has a single path for
current flow through all of its elements.
• A parallel circuit is one that requires more than
one path for current flow in order to reach all of
the circuit elements.
http://en.wikipedia.org/wiki/Series_and_parallel_circuits
SERIES CIRCUIT
• CURRENT -all elements in a series connection
have equal currents.
• VOLTAGE – Resistors with different values will
have DIFFERENT voltages
• All of the individual voltage drops across
resistors should equal the voltage across the
battery
• Total Resistance of Circuit - To find the total
resistance of all the components, add together
the individual resistances of each component
http://en.wikipedia.org/wiki/Series_and_parallel_circuits
SERIES CIRCUIT
• Total Resistance
To find the current, use
Ohm's law
To find the voltage across any
particular component
SERIES CIRCUITS
• A series circuit is a circuit in which
resistors are arranged in a chain, so the
current has only one path to take. What
happens if one device fails?
• As more resistors are added the total
resistance goes up. What does this do to
current?
http://physics.bu.edu/py106/notes/Circuits.html
PARALLEL CIRCUIT
• CURRENT - Resistors with different values will
have DIFFERENT current readings
• VOLTAGE - Voltages across components in
parallel with each other are the same
• TOTAL RESITANCE OF CIRCUIT - To find the
total resistance of all the components, add
together the individual reciprocal of each
resistance of each component, and take the
reciprocal of the sum:
http://en.wikipedia.org/wiki/Series_and_parallel_circuits
PARALLEL CIRCUIT
• Total Resistance
To find the total current, I,
use Ohm's Law
To find individual current
To find VOLTAGE
Ii= V/Ri
V= IiRi
http://en.wikipedia.org/wiki/Series_and_parallel_circuits
PARALLEL
• A parallel circuit is a circuit in which the resistors
are arranged with their heads connected
together, and their tails connected together. The
current in a parallel circuit breaks up, with some
flowing along each parallel branch and recombining when the branches meet again. What
happens is one device fails?
• As resistors are added in parallel, total
resistance goes down. What does this do to
current?
http://physics.bu.edu/py106/notes/Circuits.html