Transcript Electric Circuits

Electric Circuits
 An electric circuit is a
complete, closed path
through which a continuous
charge can flow.
 A circuit always begins and
ends in the same place. It
forms a loop.
Electric Circuits
 All electric circuits have:
1.
2.
3.
4.
a voltage source
a conductor
a switch
an electrical device
Electric Circuits
 An electric device uses electrical
energy to do work.
 All loads offer some resistance to
electric currents and cause the
electrical energy to change into
another form of energy, such as
light, heat, or kinetic energy.
Electric Circuits
 Did you know???
 Your body is controlled by a large
electric circuit. Electrical impulses
from your brain control all the
muscles and organs in your body.
 The food you eat is the energy source
for your body’s circuit,
 your nerves are the wires,
 and your muscles and organs are the
loads!
Electric Circuits
 Types of circuits
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Series circuits
Parallel circuits
Combination circuits
Short circuit
Electric Circuits
 A series circuit is a circuit in
which all parts are connected in
a single loop.
 The charges traveling through a
series circuit must flow through
each part and can only follow
one path.
Electric Circuits
 All the loads in a series circuit share the
same current. Because the current in all the
light bulbs is the same, the bulbs glow with
the same brightness.
If you add more bulbs, the
resistance of the entire
circuit
would increase and the
current would decrease. All
the bulbs would get dimmer.
Electric Circuits
 Some series circuits use a load as a switch.
For example, the automatic door at the store
is operated by a series circuit with a motor
that opens the door and a photoelectric
“eye” that acts as an on-off switch.
Electric Circuits
 For charges to flow in a series
circuit, all the loads must be
turned on and working.
 Charges pass through one load
after another, in order, around
the circuit.
 IF ONE LOAD IS BROKEN OR
MISSING, THE OTHER LOADS
WOULD NOT WORK.
Electric Circuits
 A parallel circuit is
a circuit in which
different loads are
located on
separate branches.
Because there are
separate branches,
the charges travel
through more than
one path.
Electric Circuits
 The loads in a parallel
circuit do NOT have the
same current in them.
 Instead, each load in a
parallel circuit uses the
same voltage. The full
voltage of the battery is
connected to each bulb,
so each bulb glows at full
brightness.
Electric Circuits
 You can connect loads that require
different currents to the same parallel
circuit.
For example, you can connect a
hairdryer (that requires a high
current) to the same circuit as
a lamp (which requires less
current.)
Electric Circuits
 Broken wires or water can cause
short circuits. A short circuit occurs
when charges bypass the loads in the
circuit.
 When the loads are bypassed, the
resistance of the circuit drops and the
current in the circuit increases.
 If the current increases too much, it
can produce enough thermal energy
to start a fire.
Electric Circuits
NEVER
connect a
battery only
to itself.
Short circuits
start
dangerous fires
every day!
Electric Circuits
 Circuit Safety: A
fuse contains a thin
metal strip that the
charges flow
through. If the
current is too high,
the metal in the fuse
warms up and melts.
A break in the circuit
is produced and the
current stops
flowing.
Electric Circuits
 Circuit Safety: A circuit
breaker is a switch that
automatically opens if
the current in the
circuit is too high.
 If the current is too
high, a strip of metal in
the circuit breaker
warms up and bends
away from the wires in
the circuit.
Electric Circuits
 A device that acts like a
miniature circuit breakers is
a ground fault circuit
interrupter (GFCI). It
compares the current in one
side of an outlet with the
current in the other side.
 If there is a difference, it
opens the circuit and you
must push the reset button
to close it again.