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Electricity and Magnetism

Talking your way through equations

Teaching Guidance for 14-16 Supporting Physics Teaching

Equations need to make sense

Equations, such as I = VR, are very important tools in physics. They summarise relationships in a precise and economical way and allow us to carry out simple calculations. One problem for many students in school is that they learn how to substitute values into an equation but have little sense of the story of the equation – what the equation is actually telling us.

To get round this learning challenge, whenever you're using an equation, ask the students to talk through how the equation connects the variables:

Teacher: We choose the potential difference and the resistance, and that fixes the current. Can anyone remember how these three are connected?

Teacher: Good – now what happens to the current if the potential difference drops? And if the resistance grows very large… or very small?

Teacher Tip: Talk the calculation through, don't just write it down. I = VR, so the current is xx voltyy ohm, which works out as zz ampere to 2 significant figures.

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