1. Integrated Science Unit 2: Energy & the Atmosphere
Introduction to Power
Integrated Science
Unit 2: Energy & the Atmosphere

2. Power is the rate at which energy is transformed from one form to another.
Unit: Watts (W)
1W = 1 Joule/second
Power
P = E t
Energy
Power
Time

3. Concept Questions
Which light bulb is more powerful, one that can transform 100 Joules per second, or one that transform 60 Joules per second?
Which motor is more powerful, one that can lift a certain weight 1 meter in 2 seconds, or one that can lift the same weight 1 meters in 5 seconds?

4. Example Problems
What is the power rating of a heater that can transform 5000J of energy
from electric to heat every 12 seconds?
What is the power rating of a motor that transforms 2400J of energy from electric to kinetic in 5 minutes?
How much energy is transformed by a 75W light bulb in 23 seconds?
How much energy is transformed by a 500W device in 8 minutes?

5. More Practice
1. What is the power rating of a motor if it is able to transform 5000J of energy from electric to kinetic in 30 seconds?
2. A certain light bulb is able to transform 1200 Joules of energy every 20 seconds. What is the power rating of this bulb?
3. How much energy (in Joules) is transformed from electric to heat by a 1500W toaster-oven during a 45second toasting?
4. A 250W television is accidentally left on at a home for 3 straight days. How many Joules of energy does the TV ‘use’?