1. Warm up
A light needs 3 amps to produce light the resistance of the bulb is 1.5 ohms. How many batteries do you need if each battery is 1.5 volts?
What do we mean when we say that electrical appliances use energy?

2. Key Question: How can electricity do work?
Work, Energy & Power
Key Question:
How can electricity do work?

3. What is the unit for Power?
Watt (W)
Appliances often a list the number of watts or kilowatts they use. How is this useful?
Power measures the rate of energy transfer.

4. How many joules /sec are used by a 100W light bulb?
Reminder: 1W = 1 Joule/sec
Using what you know, how can you calculate the amount of power in a circuit?
Reminder: 1 amp = 1 coulomb/sec
1 Volt = 1Joule/coulomb

5. P = VI Electrical Power P = Power (watts) V = Voltage (volts)
I = current (amps)

6. What unit does the electric company use to measure your use of electricity in so they can charge you?
Kilowatt-hour
1 Kilowatt-hour means that one kilowatt of power has been used for one hour.

7. If electricity costs $3 per Kilowatt-hour how much will it cost you to run a 5 kilowatt refrigerator fore one week?
$2520