Comparing the Rate of Energy Transfer (GCSE Physics)
Comparing the Rate of Energy Transfer
Examples of Power
Comparing the Power in Electric Motors
Question: Charlotte is comparing 2 electric motors X and Y. Each motor is lifting a mass of 300 grams, to a height of 60cm. This action takes 280 J of work to complete. Motor X lifts the mass in 70 seconds and motor Y takes 40 seconds. Calculate the power of each motor, then state which one is more powerful.
- Write out the appropriate equation.
In this case, the appropriate equation is:
Now that we have found our two values, we can see that motor Y is more powerful than motor X.We can link back to our definition for power here. Power is the rate at which energy is transferred or work is done. The faster the rate of transfer, the more powerful the object.
Comparing Costs Using Power
You may be asked to compare the costs of different energy suppliers. Here is an example:
Question: Anna is trying to decide with electricity supplier to use in her new flat.
The cost per unit is the cost for one kilowatt per hour of energy.
She would mostly use the electricity to supply her central heating. The average power of her central heating is 6800W and she keeps it on for 3 hours each day. Which electricity supplier will be the cheaper option for Anna?
- Calculate the total power Anna uses in one day.
Now that we have found our two values, we can see that Company B will be the cheaper option for Anna.
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