Transcript Section 3—Electrical Energy

Section 3—Electrical Energy
• To use electrical energy, a complete circuit
must be made
• Series Circuit—current has only one
loop to flow through
*Used in flashlights and some holiday lights
(Circuit types continued)
• Open circuit—when any part of a series
circuit is disconnected, no current flows
through the circuit
– Ex: when 1 X-mas bulb is out, the whole
string is out!!
Parallel Circuits
• Parallel circuits—contain two or more
branches for current to move through.
• Advantages:
– When one branch of the circuit is opened, the
current continues to flow through other
branches
– Ex: rooms in houses, cars, etc.
– Fig. 18 on pg. 210
Household Circuits
• In most homes, wiring is organized and
logically connected
• Wiring is hidden behind walls, under
floors, etc.
• Standard voltage difference in US is 120 V
• There is a main switch and circuit
breaker/fuse box for homes
• Parallel circuits branch out to
rooms/appliances
(more on household circuits)
• Many houses draw current from the same
circuit
• As the amount of current increases, so
does the amount of heating in the wires
• If wires get too hot, insulation melts and
bare wires can cause a fire
• For protection, homes have fuses or a
circuit breaker
Fuses and Circuit Breakers
• Fuses—small pieces of metal that melt if
current becomes too high, and causes a
break in the circuit, current flow stops
• Circuit breaker—contains a switch to
flip and open the circuit, stopping the flow
of current/usually can be reset by moving
switch to its “on” position
Electrical Power
• Electrical power—the rate at which
electrical energy is converted to another
form of energy
– Used by appliances/varies
– Calculating Power:
POWER = CURRENT X VOLTAGE
DIFFERENCE
OR
P(watts) = I (amperes) X V (volts)
Electrical Energy
• The amount of electrical energy you use
depends on two things:
– Power required by appliances in your home
– How long the appliances are used
– Calculating Energy:
• ENERGY = POWER x TIME
OR
• E(kWh) = P (kW) x T(h)
Kilowatt Hours
• Kilowatt-hour = the unit of electrical
energy
One kilowatt= 1,000 Watts
SECTION REVIEW QUESTIONS