Download presentation

Presentation is loading. Please wait.

Published byMitchell Jones Modified over 6 years ago

1
Power and Energy

2
Power Power means work over a time period Units = Watts Electric power is measured in Watts

3
Power Power = Current x Voltage Watts = Amperes x Volts P = I x V 1 kilowatt = 1000 watts

4
P = I x V V = I x R Combined: P = I 2 R P = V 2 / R AND

5
Problem 1 A CD player has 0.25 A of current running through it and runs on a 9 V battery. How much power does it use?

6
P = V x I P = 9 V x 0.25 A P = 2.25 W

7
Problem 2 How many watts of power does a TV use if its total resistance is 50 ?

8
V = 120 V (house current) R = 50 P = V 2 /R P = 120 2 /50 P = 14400/50 P = 288 W

9
The Cost of Electrical Energy

10
Power and Energy Electrical power costs $ You are charged by your rate of power usage By Kilowatt Hours (kWh)

11
Kilowatt Hours Energy = Kilowatt Hour 1 Kilowatt Hour equals consumption of 1 Kilowatt of power in 1 hour.

12
Kilowatt Hours E = P x t kWh = Kilowatts x time Cost = Rate x kWh Rate varies: 2.25 ¢ to 8.9 ¢

13
Problem How much does it cost to run a 200 W refrigerator in a month if it runs 4.5 hours per day? (rate = 8.2 ¢/ kWh)

14
Solution E = P x t t = 4.5 hrs X 30 days = 135 hrs P = 200 W = 0.2 kW

15
Solve E = 0.2 kW X 135 h = 27 kWh Cost = 8.2 ¢/kWh = 8.2 X 27 = 221.4 ¢ = $2.21

16
Problem: Assume the cost of electricity is 13 cents per kilowatt -hour. Calculate the energy used and its cost for the use of the following items: a. 4 Watt night light for 8 hours b. 1300 Watt microwave for 10 minutes c. 60 Watt light bulb 6 hours a day for one year d. 300 Watt refrigerator for 3 hours a day for one month

17
Assume the cost of electricity is 17 cents per kilowatt -hour. Calculate the power, energy used and its cost for the use of the following items connected to a 120 Volt electric outlet: a. 0.5 Amp computer monitor for 12 hours b. 10 Amp hair dryer for 5 minutes c. 3 Amp electric drill for 30 seconds d. 25 Amp electric clothes dryer connected to 240 Volts for 30 minutes

Similar presentations

© 2022 SlidePlayer.com Inc.

All rights reserved.

To make this website work, we log user data and share it with processors. To use this website, you must agree to our Privacy Policy, including cookie policy.

Ads by Google