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A kettle uses 100W of power if it transfers 1,000J of energy in 10 seconds.

# Electricity - The Usefulness of Electrical Appliances

This GCSE Physics Electricity quiz will challenge you on the usefulness of electrical appliances. It is almost impossible to spend a single day at home without using several different electrical appliances - they have completely changed the way people live since the end of the second world war. For example, television sets and radios were rare, only the most well-off people could afford them. Nowadays, most homes have several TVs and radios (the latter are often built into mobile phones and smartphones). At the same time, another electrical device that is common did not even exist - home computers. Electrical appliances are great when they are working, but it's really annoying when there is a power cut or the battery is flat!

1.
Which of the following items use electricity in the home?
Book
Chair
TV and computer
Hang your head in shame if you got that one wrong!!
2.
Which does not normally rely on electricity?
Water tap
Wireless router
Tumble dryer
Oven
OK, that's the end of the warm up questions!
3.
If a 3 kW kettle is switched on for 3 minutes, when compared to a 2 kW toaster switched on for 5 minutes, which uses more energy?
Kettle
Toaster
They use the same amount of power
More information is needed to discover which appliance uses the most power
Using simple ratios often can help to work the answer out - three times three for the kettle as opposed to two times five for the toaster. Working it out correctly, the kettle uses 0.15 kWh whilst the toaster uses 0.17 kWh of power
4.
Another kettle has a power rating of 3 kW of power and transfers 2 kW of that into heat energy to boil water. How efficient is the kettle?
33%
50%
66%
75%
Efficiency is calculated by dividing the output by the input and converting the resulting fraction to a percentage by multiplying by one hundred
5.
What is an advantage of using a kettle instead of a pan on a gas cooker to boil water?
Easier to pour the hot water
Faster to boil water
There is no advantage
More efficient and often faster to boil water
Even with a lid on the pan, more of the energy will end up in the water when using the kettle
6.
Which would be safest and most efficient for toasting bread?
Cooker hob
Toaster
Oven
Barbecue
Minimizing risk and maximizing efficiency is always a major factor in the design of appliances for specific purposes. Not all exam questions will make it as obvious as this, so be on the lookout for this type of question in your GCSE exams and tests
7.
Which appliance would work if the electricity was not working in a house?
Wind-up torch
Solar hot water heater
Petrol lawn mower
All of the above
Whilst many appliances run off mains electricity, it is possible to rely on other sources of energy to power appliances. Finding a balance between appliances could not only save you money but also save harmful gases from being released into the atmosphere as a result of how electricity is generated by power companies. In this case, an electric lawn mower would be the compromise - you can't cut the lawn during a power cut but does that really matter?
8.
What is a disadvantage of an oven?
Large capacity means it is not efficient for cooking small items
Can only heat at one temperature
Large capacity for cooking multiple items
Has a timer
As ovens have large capacities, it is sometimes inefficient to cook small items in it. Instead, see if it is possible to use a microwave or a slow cooker as both have smaller capacities and are more efficient for smaller items
9.
How much power does a kettle use if it transfers 1,000 joules of energy in 10 seconds?
1 W
10 W
100 W
1,000 W
power = energy transferred divided by the time taken to transfer the energy. One watt is a rate of transfer of energy of one joule per second
10.
If an electric hob uses 75 W of power in 300 seconds to boil water in a pan, whilst a kettle uses 100 W to boil the same mass of water in 150 seconds, which is the more energy efficient appliance to use for this process?
Kettle
Hob
They use the same amount of energy
It is impossible to work out
This is a quantitative variation of question 5. From the equation linking energy, time and power you can calculate that the kettle uses only 15,000 J whereas the hob uses 22,500 J
You can find more about this topic by visiting BBC Bitesize - Domestic electricity

Author:  Martin Moore