Hi

I’m studying physics electricity and there are a lot of formulas. I want some ideas of how and what formula to use.

Thanks

Hi

I’m studying physics electricity and there are a lot of formulas. I want some ideas of how and what formula to use.

Thanks

Kia ora Seetai1,

Good question, this is a key part of NCEA Physics and a consistent approach should help you make a start on all of your calculation questions.

I would recommend the **GUESS** method. I’ll walk you through it below with an example, and link a L1 video example that might help you see how it works.

*Example - What voltage would be measured across a 12 ohm bulb, if there was a current of 3.0 Amps through the bulb?* (You might find it useful to highlight quantities in the question)

G - **Given** - write down all quantities (using correct symbols) and values have you been given in the question eg. R = 12 ohms, I = 3.0A

U - **Unknown** - write down the symbol for the quantity you are being asked to find eg. V=?

E - **Equation** - look at the equation list and find an equation that includes the **unknown** and in which every other symbol is one of your **given** quantities. It might help you to tick terms on the resource sheet until you find an equation in which every symbol is ticked. In our example we would find V=IR covers our given and unknown symbols. You might need to re-arrange the equation to isolate the unknown quantity on one side.

S - **Substitute** - replace each symbol with its corresponding value. So V=IR becomes V= 3.0 x 12

S - **Solve** - perform the calculation and write your answer, with appropriate units eg. V = 36 Volts. You should round to an appropriate number of significant figures but I won’t cover that here as it does not relate directly to your question, and you are rarely marked down for it in the exam.

You will be given a copy of the resource sheet in the exam.

Be aware, some merit or excellence questions will require you to use one equation to calculate a value that you then use in a second equation to get your final answer.

I hope that helps. Best wishes for your exam.

Memorizing equations actually kills the joy of learning electricity. Just get some resistors, 4.5 V battery and a DMM a few hookup wires Build simple series and parallel circuits, measure volts, amps, net resistance and then look Ohms laws. All will make sense to you. This is a kind of ‘sticky learning’.

Thank You So Much

This really helps

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