04/10/2023
LO:
Energy and power
What is power?
Some
Most
All
Physics 2b
• Be able to explain the difference
between energy and power
• Be able to describe the link between power,
fuel use and the cost of using domestic
appliances
• Be able to recall the equations to calculate power
Keywords:
Power rating, watt, kilowatt, kilowatt hour (kWh)
BLP objective
Collaboration
Respecting and recognising
other view points, adding to
a drawing from the strength
of teams
Making Links
Seeing connections between
events and experiences,
building patterns.
04/10/2023
Literacy objective
• Can you use standard
English to share your
opinion with the class?
• Can you write your
answers using standard
English, scientific
keywords and taking
care of spellings and
punctuation?
Starter
On your post it write
down your definition
of power.
Then write it much
more simply so you
can explain it to a
Year 5 student.
Power
Appliances in your
home have power
ratings these are
given in watts. The
power rating tells you
how much energy is
transferred to the
device a second.
Power
The more powerful an
appliance, the faster
the rate at which it
transfers energy.
Make a list of ten
appliances you used
yesterday – put them
into order of how much
power they used!
Power Calculations
Calculate the power
1. A microwave transfers 30kJ in two minutes
2. My nutribullet transfers 800kJ in 30 seconds
3. I spent 7 minutes straightening my hair this morning,
my straighteners transferred 252kJ of energy. What is
their power?
Extension
1. My toaster was on for 2 minutes, it has a power rating
of 103W. How much energy was transferred?
2. My tumble dryer has a power of 500W and was used
for 45 minutes – what was the energy transferred?
Investigating power
Around the lab are a selection of different
appliances. You need to find out its power by
looking at the labels and fill in the table. Use the
unit on the appliance.
You have 15
minutes – you
need to do all
questions except
the extension –
we’ll do these
later.
Paying for electricity
When you pay for electricity
you are paying for the
electricity company to
generate a voltage that we
call the mains electricity. You
are then charged for the
number of hours you use
your appliances.
Paying for electricity
Energy use is calculated in
kilowatt hours (kWh) or
joules – this is the unit
electricity companies use to
calculate your bill.
An example calculation
An oven with power rating of 12 kW is
used for 1 hour
Energy used in kWh = 12kW x 1 hour
= 12kWh
An example calculation
A laptop with power rating of 6 kW is
used for 3 hours
Energy used in kWh = 6kW x 3 hour
= 18kWh
An example calculation
A microwave with power rating of 7000 W is
used for 87 minutes
Calculating the electricity bill
Each kWh has a charge, for example 7p.
You just multiply the number of kilowatt
hours by the cost per unit.
Calculating the electricity bill
Complete the extension activity on the
practical worksheet.
After answering question 2 – calculate the
cost of running each appliance.
The month has 30 days – calculate the
months electricity bill.
Energy saving bulbs
These two bulbs have the same brightness
but the one on the right has a much lower
power. Why? Use your definitions of your
keywords to formulate your answer.
Learning consolidation
Describe the link between power, fuel use
and the cost of using appliances.