Electric Power AC and DC Electricity Key Question How much does electricity cost and what do you pay for Students read Section 203 AFTER Investigation 203 Electric Power AC and DC Electricity ID: 596479
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Slide1
Electric Power, AC, and DC ElectricitySlide2
Electric
Power, AC, and DC Electricity
Key Question:
How much does electricity cost and what do you pay for?
*Students read Section 20.3 AFTER Investigation 20.3Slide3
Electric
Power, AC, and DC Electricity
The
watt
(W) is a unit of power. Power is the rate at which energy moves or is used.Since energy is measured in
joules
, power is measured in joules per second.
One joule per second is equal to one watt.Slide4
Reviewing
termsSlide5
Power
in electric circuits
One watt is a pretty small amount of power.
In everyday use, larger units are more convenient to use. A
kilowatt (kW) is equal to 1,000 watts.The other common unit of power often seen on electric motors is the horsepower.One horsepower is 746 watts.Slide6
Power
P = VI
Current (amps)
Voltage (volts)
Power (watts)Slide7
Calculate
power
A light bulb with a resistance of 1.5Ω is connected to a 1.5-volt battery in the circuit shown at right.
Calculate the power used by the light bulb.Slide8
Paying
for electricity
Electric companies charge for the number of kilowatt-hours used during a set period of time, often a month.
One
kilowatt-hour (kWh) means that a kilowatt of power has been used for one hour. Since power multiplied by time is energy, a kilowatt-hour is a unit of
energy.
One kilowatt-hour is 3.6 x 106 joules.Slide9
Calculate
power
Your electric company charges 14 cents per kilowatt-hour. Your coffee maker has a power rating of 1,050 watts.
How much does it cost to use the coffee maker one hour per day for a month?Slide10
Alternating
and direct current
The current from a battery is always in the same direction.
One end of the battery is positive and the other end is negative.
The direction of current flows from positive to negative. This is called direct current
, or
DC
.Slide11
Alternating
and direct current
If voltage alternates, so does current.
When the voltage is positive, the current in the circuit is clockwise.
When the voltage is negative the current is the opposite direction. This type of current is called alternating current, or AC.Slide12
Alternating
and direct current
AC current is used for almost all high-power applications because it is easier to generate and to transmit over long distances.
The 120 volt AC (VAC) electricity used in homes and businesses alternates between peak values of +170 V and -170 V at a frequency of 60 Hz.
AC electricity is usually identified by the average voltage, (120 VAC) not the peak voltage.Slide13Slide14
Application: Wiring in Homes and BuildingsSlide15
Application: Wiring in Homes and Buildings