1. Calculating Electricity
Ohm’s Law and Power Equation

2. Relationship between voltage, current, and resistance
Ohm’s Law
Relationship between voltage, current, and resistance

3. Ohm’s Law E represent voltage, (E is short for electromotive force)
I represent current measured in amperes
R represent resistance measured in ohms

4. Ohm’s Law
Relationship between E, I, and R
E = I x R

5. Ohm’s Law
Assume that 10 A of current flows in circuit having a total resistance of 11 ohms. What is the source voltage?
E = I x R

6. Ohm’s Law
Using the formula
E = I x R
E= 10 A x 11ohms
E = 110 volts

7. Ohm’s Law
Assume that there are 6 amps of current flowing through a 120 volt circuit. What is the resistance?
R = E ÷ I

8. Ohm’s Law Using the formula R = E ÷ I R = 120 volts ÷ 6 amps
R= 20 ohms

9. Ohm’s Law
Assume that you need to know how much current is flowing through a 115 volt circuit containing 25 ohms of resistance. What is the amperage of the circuit?
I = E ÷ R

10. Ohm’s Law Using the formula I = E ÷ R I = 115 volts ÷ 25 ohms
I = 4.6 amps

11. Relationship between watts, amps, and volts
Power Equation
Relationship between watts, amps, and volts

12. Power Equation
P for watts (P represents power)
I for amps
E for volts

13. Power Equation
Relationship between P, I, and E
P = I x E

14. Power Equation
Assume that .83 amps of current flows through 120 volt circuit. How many watts of electrical power are being used?
P = I x E

15. Power Equation Using the formula P = I x E P = .83 amps x 120 volts
P = 99.6 watts of power

16. Power Equation
Assume that there are 5, 100 watt light bulbs being operated on a 115 volt circuit. How many amps of current are flowing through the circuit?
I = P ÷ E

17. Power Equation Using the formula I = P ÷ E I = 500 watts ÷ 115 volts
I = 4.35 amps of current

18. Power Equation
Assume that there is a 1200 watt coffee pot pulling 10 amps. What is the source of voltage?
E = P ÷ I

19. Power Equation Using the formula E = P ÷ I E = 1200 watts ÷ 10 amps
E = 120 volts