# What is the most effective use of the equation sheet?

When any question requires a formula, it is best to write down what is given to you in symbol form. You can then easily select the relevant equasions from the data sheet. Remember the multipliers! Take for example, the basic question below: A new washing machine consumes a charge of 18000C every 300 seconds. It has a power rating of 13.8kW. What is the resistance of the washing machine? Q=18000   t=300  P=13800 It can now easily be seen that the most relevant equasions are P=IV, V=IR and Q=It. it is now key to manipulate these into a manageable form. Try to do this without using values as, once mastered, this skill tends to avoid mistakes in a pressured situation. it can firstly be seen that, as we have no value for V, we can substitute IR into the equasion for P, resulting in the equasion P=I2R. I can then be substituted for Q in the same manner, resulting in P=(Q/t)2R. this can finally be rearranged and values can be substituted. Although this appears complex, this method will become second nature with practice and allow you to address much more challenging questions without error.

Answered by Connor W. Physics tutor

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