Idea 4of 9Builds onThe flowThe thermal tax
Nothing is used up
Is the current leaving a bulb the same as entering?
Today you'll discover
- what the current does inside a bulb
- what the bulb actually spends
- two rules the loop can never break
Think firstTwo bulbs in one loop. Compare the wires
The current enters the first bulb at 1 A. What leaves it?
Decide first, then press Next. Compare the arrowheads before and after each bulb.
A loop of wire with a battery and two bulbs along the top, arrowheads of the same size on every wire. After a prediction, the wires before and after the bulbs are labelled with the same current, then the volts across each bulb are printed, half the battery's each. The last step asks which of two identical bulbs in one loop is brighter.
See the whole ideathe big idea and the key word, in one place
The big idea
The current is the same all round; voltage gets spent.
Easy to get wrongThe first bulb does not take the current first and leave less for the second. One flow, one size, everywhere in the loop.
Key word
- Kirchhoff's laws
- the current into any junction equals the current out; round any closed loop, the voltages spent add up to the voltage supplied
About this modelCharge is never used up: what leaves the battery comes back. Volts are what get spent.
Charge is never used up: what leaves the battery comes back. Volts are what get spent.
Ready to use it?
- Give the current at any point in a described single loop, and the voltage each equal bulb takes.