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