1. 1 DC ELECTRICAL CIRCUITS POWER

2. 2 DC ELECTRICAL CIRCUITS Power is the rate at which electrical work is done in a specific amount of time. Earlier you learned that a joule is equal to the amount of work done by one volt of EMF in moving one coulomb of charge with no regard to time. Power is the measure of joules of work per unit of time, the unit of power is the Watt. Power is the rate at which electrical work is done in a specific amount of time. Earlier you learned that a joule is equal to the amount of work done by one volt of EMF in moving one coulomb of charge with no regard to time. Power is the measure of joules of work per unit of time, the unit of power is the Watt.

3. 3 DC ELECTRICAL CIRCUITS The watt is equal to one joule per second. The joule is equal to.738 foot pounds ( about ¾ of a pound), the watt is also equal to.738 foot pounds (one pound lifted one foot) of work per second. The watt is equal to one joule per second. The joule is equal to.738 foot pounds ( about ¾ of a pound), the watt is also equal to.738 foot pounds (one pound lifted one foot) of work per second.

4. 4 DC ELECTRICAL CIRCUITS The unit of mechanical power is the horsepower, one horsepower is equal to 550 foot pounds per second, or 746 watts.

5. 5 DC ELECTRICAL CIRCUITS Power is directly proportional to both current and voltage. The symbol (P) is used to represent power in equations. The formula for power is: P = I x E Power is directly proportional to both current and voltage. The symbol (P) is used to represent power in equations. The formula for power is: P = I x E

6. 6 DC ELECTRICAL CIRCUITS There are three formulas for every quantity in the expanded pie chart. The center of the circle is the ohms law quantities; I, R, E & P, in this chart has its own color coded section. There are three formulas for every quantity in the expanded pie chart. The center of the circle is the ohms law quantities; I, R, E & P, in this chart has its own color coded section.

7. 7 DC ELECTRICAL CIRCUITS Here are the formulas to solve for amperage based on the values given. If you have the wattage and voltage of a circuit, to solve for I which formula would you use? Here are the formulas to solve for amperage based on the values given. If you have the wattage and voltage of a circuit, to solve for I which formula would you use?

8. 8 DC ELECTRICAL CIRCUITS To solve for (R) you would use one of the three formulas in the pie chart depending on the values given. P = 1000W, I = 5A what is the resistance? To solve for (R) you would use one of the three formulas in the pie chart depending on the values given. P = 1000W, I = 5A what is the resistance?

9. 9 DC ELECTRICAL CIRCUITS To solve for (E); P = 200W, R = 25 Ω, what is the voltage? To solve for (E); P = 200W, R = 25 Ω, what is the voltage?

10. 10 DC ELECTRICAL CIRCUITS To solve for (P); E = 120V, R = 40 Ω, what is the wattage? To solve for (P); E = 120V, R = 40 Ω, what is the wattage?

11. 11 DC ELECTRICAL CIRCUITS A HEATING UNIT IS RATED TO 1600 WATTS WHEN CONNECTED TO A 240 VOLT CIRCUIT, HOW MUCH CURRENT WILL THE UNIT DRAW?

12. 12 DC ELECTRICAL CIRCUITS A CIRCUIT WITH A 100 OHM RESISTOR HAS A CURRENT OF 6.8 AMPS, WHAT IS THE VOLTAGE? IS A RESISTOR RATED TO HALF A WATT LARGE ENOUGH FOR THIS CIRCUIT? A CIRCUIT WITH A 100 OHM RESISTOR HAS A CURRENT OF 6.8 AMPS, WHAT IS THE VOLTAGE? IS A RESISTOR RATED TO HALF A WATT LARGE ENOUGH FOR THIS CIRCUIT?

13. 13 DC ELECTRICAL CIRCUITS Resistors are rated by wattage, and as you can see here the smaller the resistor the lower the wattage rating.

14. 14 DC ELECTRICAL CIRCUITS As you know incandescent light bulbs are rated in wattage, fluorescent bulbs are also rated in wattage and now LED bulbs are becoming more and more popular. Given that the voltage and current remain the same how do you select the right bulb for the desired illumination. As you know incandescent light bulbs are rated in wattage, fluorescent bulbs are also rated in wattage and now LED bulbs are becoming more and more popular. Given that the voltage and current remain the same how do you select the right bulb for the desired illumination.

15. 15 DC ELECTRICAL CIRCUITS