Module 1 – Energy and Power (ED)

Energy 101: power

We can consider energy and where is comes from such as the sun, and other sources such as fossil fuels. Then we can also talk about energy relating power how much power do things need to operate. A battery holds power and appliance uses power.

Understanding energy ratings

Appliances come with an energy rating, for example, a kettle typically has a 3,000 watts rating and a fridge typically uses 300 to 800 watts of electricity. These details are found under the appliance or at the back. Sometimes in a bold sticker on the front in the shop.

Let’s take a brief look at energy relating to power usage and then consider where we get our energy from, such as energy stations, energy suppliers and then ultimately the natural sources of energy.

A watt is the smallest unit of measurement indicating how much power is needed to make it work.

Group Discussion

Right now, where you are sitting, look around you and quickly take note of everything that is currently using power. Create a list or combine these observations in a discussion with the class. Can you investigate the energy rating the items have (tip: check underneath or on the back)

In the area below write down:

• Items that are currently using power in the room
• Did you investigate the items energy rating? What were they? 

Understanding how to convert watts to kws

Example:

By using the table above we can convert watts into kWs. 

• 3,000 watts = 3 kW | Solution 3000 / 1000
• 800 watts = .8 kW | Solution 800 / 1000

Tip: Look at the first line of the table and you can see that 1 kW = 1,000 watts

• Divide the power value by 1000

Question: 

Use the table of measurements to decipher the watts into the equivalent kWs. 

• Sort the answers below into the correct order
  First | 412 watts =
  Second | 652 watts =
  Third | 4,060 watts =  

Converting kilowatt (kW) into kilowatt-hour (kWh)

Now that you have converted watts into kW we can than turn that into kWh. This is a great place to start understanding energy consumption.

Convert the kW into kWh by multiplying the kW by the number of hours it is used for.

Example

• A fridge uses 800 watts. Convert this into kW (800 / 1000 = .8)
• A fridge is on 24hrs and it uses .8 kW
• Multiply .8kW by 24 to calculate the kWh usage of energy.
• .8 x 24 = 19.2 kWh

Fill in the blanks below

Practical Activity

Fill a kettle with cold water from the tap, time how long it takes to boil. A typical kettle uses 22000w to 24000w

Write your findings into the blanks below demonstrating the total kWh of a kettle.

• Don’t have a kettle to boil. Do this at home and bring the time to your next class. 
• For the purpose of the activity when you don’t have a kettle use the boil time of 6min

Hint: A kettle will not run for a full hour so you will need to break down the hour into minutes to collect a more precise number. 

• The number to use for 1 minute is 0.01666
• We get this number by
  1 (An hour) / 60 (minutes in an hour) = 0.0166666666666667