# Electricity Electricity C H AP TE R 17. 3 Section 3 Electrical Calculations Ohms Law shows the relationship between resistance, voltage, and current. Ohm noticed that for each

material the ratio between voltage and current was Ohms Law Formula Resistance=Voltage/Current R=V/I OR Voltage= current x resistance V=I x R

V R I Ohms Law As voltage increases, current increases direct relationship As resistance increases, current

decreases Inverse relationship Graphs on page 490 in you textbook illustrate Electric Power Electric Power-the rate at which electrical energy is changed into other forms of energy The unit to measure power is

the Watt (W). For larger numbers we use a kilowatt (kW) The brighter the light bulb is the more quickly it uses energy, therefore the more Electric Power Formula Electrical Power= Voltage x Current

P P=VxI V I Measuring Electrical Energy You can save energy by using appliances with lower

power ratings. The unit for energy is still the Joule (J) Often the power company will use Kilowatt-hour (kW-h) to measure the energy used. This makes sense, it is a unit of power x time and that equals energy. Electrical Energy Formula

Electrical Energy = power x time E E=Pxt P t