AC Theory
Power & Energy Quiz
Try a few calculations based on Power and Energy, using the information on the "Power and energy" page. Some are easy, some are not. Because more than one formula may be needed to solve some of the problems its important to remember to use the correct formula at the right time.
Before starting, think about these few tips, they will make the problems easier if followed carefully.
1. Work out the answers using pencil and paper; otherwise you WILL get mixed up half way through and end up with the wrong answer.
2. Of course the answer is not just a number, it will be a certain number of Watts or Joules, don't forget to show the correct unit (e.g. W mW J etc.) or your answer is meaningless.
3. Convert all sub units such as mW to Watts before you put them into the appropriate formula. A slip up here can give really stupid answers, thousands of times too big or too small.
To help you on the right track why not should download our "Maths Tips" booklet, which shows you how to use your calculator with exponents and engineering notation to deal with those sub-units and get the right answer every time.
Not got a scientific calculator? The "Maths Tips" booklet explains what you need (and what you don't need so you don't spend your money unnecessarily). If you don't want to buy a scientific calculator, you can always pick up a free one on the net. PC users can try Calc98 from www.calculator.org/download.html. Whichever calculator you choose remember that you should read the instructions to become familiar with the working methods you should use as these do vary from calculator to calculator.
OK so now you have read these instructions, you are ready to start.
Note: If you are using Calc98 for your calculations you need to set the View>Option>Display menu to Engineering (under the "Decimal" choices) and it would be a good idea whilst you are in this menu to select 2 from the Decimals drop down box to set the number of digits after the decimal place. This will round your answer down to two decimal places which is sufficiently accurate for most uses and stops you getting silly answers such as 4.66666666667mW, which would be far too accurate for any practical scale of measurement we would be likely to use.
Power and Energy Quiz
(Calculate your answers with pencil, paper and calculator, then check your answers below.)
1.
What is the power dissipated by a circuit that passes a current of 1.6A when a voltage of 6V is connected across it?