Using the simulation in class / Teaching the relationship between energy and voltage

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HEADLINE LEARNING POINTS

  • The amount of energy a charge is carrying is called the voltage or potential at that point

  • The potential decreases when charges lose energy in the bulb

  • Charges just go round and round, but energy ends up spreading out into the surroundings

UNDERSTANDING

  • At a physical level, batteries run out of chemicals to react - once all the chemicals have reacted the battery is dead

  • At a conceptual level, batteries run out of energy

  • Bulbs work because the filament gets so hot it glows

  • All the energy from the battery’s chemical store ends up increasing the thermal store of the surroundings

USING THE SIMULATION

  • Energy is represented by red stuff

  • Show that there’s energy round the charges (black dots) and energy spreading out at the bulb

  • Show that charges don’t get lost, but energy does

  • The amount of energy carried by each charge is called the voltage or potential

  • Ask students:

    • Where is the potential highest?

    • Where is the potential zero?

    • What happens to the potential as charges move through the bulb?

    • Why does the potential drop through the bulb?

SUBTLETIES

  • Individual charges don’t really carry energy, but it’s really helpful if we pretend they do because it helps us visualise voltage and power

  • For that matter, energy is just a number, so it can’t ‘fill up’ any ‘stores’ - it just depends where you draw the line for helpful metaphors

  • Potential is really a property of a point on the circuit, not of individual charges

  • Even though potential at a point is often only introduced in more advanced course, it really helps with the concept of potential difference

MISCONCEPTIONS

  • Because we talk about ‘charging’ a battery, it’s understandable for students to think that batteries run out of charge

  • Charging in this context means ‘filling up’, like a charge card that you fill up with money