A box with three light bulbs and six connections.
Three wires with aligator clips on the ends.
The idea is that by connecting the proper pairs of connectors, you can make all three light bulbs go on. Connect the green A to the red A and the A light goes on, connect the green B to the red B and the B light goes on, and the same for C. The idea is to figure out where the wires are going behind the box (this is a demonstration of how circuits work for young elementary school kids).
Do I need three batteries or can it work with only one? So far the only way I can think to hook it up using only one battery results in the A light going on when you connect the green A to any of the red connectors, etc.
(I should add that on the actual box, the connectors aren’t labelled and they aren’t in order, so you have to try connecting them different ways to figure out which pairs complete the circuits)
I should have asked if components like transistors, logic gates and such can be used, or must it be simple wiring? If the latter, then using three batteries is the only way I can think of.
No, it’s got to be just basic wires. We are talking about something I’m helping my 8 year old son build for a science project. He has to not only understand it but be able to describe how and why it works.
In that case, having three separate circuits each with its own battery is the simplest approach. Unless it’s permissible to none of the lights to come on until all the connections have been made. This can be acheived by having each correct connection pair completing a link in a series circuit. Sort of like this:
B±------A> <a—O----B> <b-----O-----C> <c------B-
B+ is the positive battery terminal, B- is the negative. The Os are the lamps and the lettered >s are the connectors. Clear as mud?
No, that wouldn’t work at all. This needs to be the kind of thing that an 8 year old can solve easily in under a minute. It’s meant more as a hands-on fun game/learning tool, not a difficult challenge.
Thanks for taking the time to look into it. I was really hoping I wouldn’t need 3 batteries. sigh.
The battery can be wired in any way I want, but I’m assuming the battery(ies) will be inside the box, wired into the circuit. Otherwise the kids would be clunking around a battery on a wire while trying to hook things up.
The idea is that the kids will be able to get all three lights turned on (at the same time) by hooking up the three wires to the various connectors until they find the right pairs.
I haven’t noticed any difference in brightness, but then I only briefly connected them all to the battery, and only just to test that they worked.
There, a simple parallel circuit. Connecting any A-A, B-B, C-C set and the corresponding bulb will light. Connect two sets, lights two bulbs. Connect three sets, all three are lit. And, since it’s in parallel, all bulbs will be of equal brightness. I believe that will work.
Sorry about the colors. I tried to stick with the ones in the picture you provided.
The problem with that is that it will light the wrong bulb if the wrong connectors are joined. For example, if you connect any of the black wires to the red C, the C bulb will light. The OP said she didn’t want that to happen.
The only problem with this circuit is that you can get bulb A to light by connecting it to ANY of the terminals on the right side, not just the A terminal. Same with B and C. I don’t see any way to accomplish the desired result without three batteries.
In the actual box, there are 8 connectors, numbered 1 - 8. Numbers 1 - 4 are red, 5 - 8 are black. Two are “dead” while the other six form three pairs which complete the circuits.
So I want it so that, say,
1 + 6 = red
2 + 8 = green
4 + 7 = blue
3 and 5 aren’t connected to anything
In your example, 1 + 6, 1 + 7 and 1 + 8 would ALL light up red… etc. I want ONLY one combination to work for each light.
I can’t imagine how this would work with one power source. If 1 is connected to the battery, 6 is red, and 7 is blue, then 1 + 6 and 1 + 7 both give a circuit for the electricity to light up a bulb.
A few mental calculations later, I’m willing to say that you provably need three distinct power sources to do what you want.
Opal, I’m afraid you are just going to have to use 3 batteries.
Look at it in the basic sense: Each light bulb is going to light up as soon as it gets a potential drop of x Volts across it. (I’m not worried about what x is at the moment).
One battery and wires, without any active circuitry, are going to give you a set of points, that are either: unconnected; at 0V; or at x Volts. Any connection that puts 0V and x Volts on opposite sides of a bulb will light it up, which will not give the unique solution you want.
I see that Q.E.D. was thinking of putting some active circuitry in the box, but I still think you would be stuck. Every point in a DC circuit would be at 0V, y Volts (I won’t assume that’s the same as x, but let’s call “y” the voltage of the battery), or at a point in between. If there are some combinations in between the two, for every path you have that would produce a lesser voltage, you will have a corresponding one that produces a larger voltage - putting too much voltage across the bulb, and taking away your unique solution.
If you want all 3 to be separate circuits, they need to be separate power cells. Furthermore, they can’t share a common ground (or any other common point in the circuit).
I wish you well with your demonstration. Hey, you could even work this in, showing what happens if you connect the ground lines (for example) of two of the bulbs, showing that either connection would then work.
Nah, I think it would be relatively trivial with the use of logic gates, or maybe even discrete transistors. If I’m feeling less lazy than I am at the moment either later today or tomorrow, I’ll try to come up with something, unless someone else beats me to it.
Yeah, but keep in mind that this has to be something an 8-year old can understand.
I’m starting to wonder if this is even possible without some fancy electronic work. You’re going to run into the problem that connecting any bulb to any power source will light that bulb. I don’t see a simple way around that.
Your other option is to munge the wires around inside the box any way you like, and give the battery to the kid. Mark one of the battery terminals red, mark one green (or don’t! your pick). If you want to be really super-controlling about it, place the battery in its own box with the heads of two nails sticking out, marked PLUS and MINUS; place the six-wire / three-bulb box adjacent. Then you’ve got a small pedestal on the left with three bulbs and six wires, a small “workspace”, and then another small pedestal with two copper nail-heads sticking out.
Kid walks up, hooks a green clip to one nail, a red clip to another. Bulb may or may not light, kid starts thinking, and you get to stand in the gym by your kid with a MISSION ACCOMPLISHED banner in the background.
Let me look at it again and see what I can come up with.