Circuits
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Posted by Danny Nicholson | Posted in Physics | Posted on 19-06-2008
Tags: AT4, bulbs, circuits, electricity, ks2, Physics, Sc4
To answer another one of the questions you submitted. Trying to explain why the brightness of bulbs in a circuit changes can be tricky. It can be helpful to imagine different analogies/models to explain what is happening.
A very nice place to start is this presentation from Skool.co.uk
A battery with one bulb connected is your standard to compare things to. Electricity flows from one end of the battery to the other, flowing through the bulb as it goes, making the bulb light up.
Adding a second bulb in series will increase the total resistance in the circuit. The bulbs will be dimmer than the single bulb.
Adding a second bulb in parallel is a different situation. You have added a second parthway for the electricity to flow, The resistance is greater than a single bulb, but is is not as high as the two bulbs in parallel. The two bulbs will be brighter.
A “cars on the highway” analogy may help explain the distinction: think of a wide highway narrowing to a one-lane bridge to cross a river. Now imagine that in order to get rid of traffic jams, the highway department builds another one-lane bridge over the river. The “resistance” (in this case analogous to the width), of both bridges stays the same, but the amount of “current” or traffic that can cross the river has increased, so the overall “resistance” of the entire system has decreased. Taken from here.
In a series circuit, each bulb you add will make the brightness of the bulbs dimmer and dimmer
In a parallel circuit, the brightness of the bulbs does not change with the addition of more bulbs (but if you added many parallel circuits, eventually all of the bulbs would dim down as you approached the capacity of the battery)
This page from the BBC KS2 Bitesize site is pretty useful.
The GCSE Bitesize page may help explain things to you too.
More Links and Resources
Here are some more links that hopefully will help with teaching circuits
The free circuit builder Crocodile Elementary is now called Yenka Basic Circuits, and you can get it here. This will let you build circuits to your heart’s content!
From BBC Science Clips, try these resources:
http://www.bbc.co.uk/schools/scienceclips/ages/6_7/electricity.shtml
(http://www.bbc.co.uk/schools/ks2bitesize/science/activities/conductors.shtml)
(http://www.bbc.co.uk/schools/ks2bitesize/science/activities/changing_circuits.shtml)
Other Links
Make an Electric Circuit Online
BBC Learning Zone – Electricity Videos
For a quick 10 minute preview, that explains some aspects of circuits. Go to Furry Elephant, and choose series or parallel circuits. It literally only allows you 10 minutes though.
Link to other Links Pages
E=TC3 6G Changing Circuits Page
E=TC3 4f Circuits and Conductors Page
