Distinguishing between current and energy
Teaching Guidance
for 11-14
Current does one thing: energy another
Wrong Track: The electric current gets used up in the bulb.
Right Lines: Energy is shifted by the action of the bulb. As the charged particles first pass through the bulb, they encounter resistance in the filament, and energy is shifted to the thermal store of the filament as it warms up and starts to glow. The charged particles continue around the circuit. Energy, and not the charged particles, is shifted by the bulb and dissipated.
Two kinds of flow
Thinking about the learning
The incorrect idea here is that when the charged particles pass through the bulb, they make the bulb light and so get used up.
Thinking about the teaching
There are two kinds of flow: electric charge and energy. The Physics narrative explains the difference. You should refer to both kinds explicitly. You may even bring the wrong tracks
thinking in explicitly, so as to focus attention on the issue:
Teacher: So, in last year's class, they thought that the charged particles got tired as they went through the bulb, and got used up
. What do you think of that?
