1. Ohm’s Law V IR Voltage Current Resistance

2. George Ohm 1827 - published the Ohm’s Law formula The formula was based on his experiments with electrical resistance. Ohm’s Law shows the relationship between voltage, current, and resistance.

3. Ohm’s Law Formula R = V I R is for resistance V is for voltage I is for current Resistance is measured in ohms. Voltage is measured in volts. Current is measured in amps.

4. Other Formulas The equation can be rearranged to solve for current and voltage. I = V R and V = IR So, if any two values are known, you can solve for the third.

5. With Constant Resistance The greater the voltage, the greater the current. So, if we double the voltage, what happens to the current? Voltage =Current

6. With Constant Voltage For a greater resistance, the current is decreased. So, if resistance is doubled, what happens to the current? Resistance Current=

7. Example Solving for Resistance An automobile headlight is connected to a 12-volt battery. If the resulting current is 0.40 amps, what is the resistance of the headlight? Answer: 30 Ω

8. Example Solving for Voltage In order for a waffle iron to operate efficiently, a current of 12 A must flow through its coils. If the resistance is 10 Ω, what must the voltage be? Answer: 120 V

9. Example Solving for Current You light a light bulb with a 1.5 volt battery. If the bulb has a resistance of 10 Ω, how much current is flowing? Answer: 0.15 A

10. References Prentice Hall Physical Science Textbook pgs. 658 – 659 ISBN: 0-13-062649-X http://www.ndt- ed.org/EducationResources/HighSchool/El ectricity/ohmslaw.htmhttp://www.ndt- ed.org/EducationResources/HighSchool/El ectricity/ohmslaw.htm