So a microphone works as follows. Sound waves strike a surface, causing the surface to vibrate. The surface is attached to a magnet inside an electric coil. As the magnet vibrates, it creates electric pulses in the coil. Those electric pulses are then sent down a wire, until they can either be converted to digital data or reach a speaker–which is basically a microphone in reverse.
This would be, for a children, a good opportunity to learn scientific facts: that sound is a series of compression waves, with the frequency and amplitude determining the pitch and loudness of the sound. Also that electric current is generated by moving a magnet with a coil of wire (i.e. Faraday’s Law). So now I’m wondering, what other ordinary stuff makes a good physics or chemistry lesson?
I would take that another step further and then explain that those sound waves then vibrate your eardrums which is how you hear the sound. Electric guitars and even your voice all work on very similar principles. You can even show how waves move by tossing something in a pool of water.
Something else you can do is point a remote (IR only, RF won’t work**) at a digital camera*. The camera will pick up the IR light and display it. We all know how remotes work, but it’s fun to see it.
*This won’t work with all digital cameras, but it will on most of them, including your cell phone. They can detect IR and they’ll display it as a purplish white color.
**If you’re using a TiVo remote, use the volume button, TiVo uses RF signals, which is why the TiVo remote doesn’t need line of sight to work.
Another one my daughter had fun with was playing with my Non-contact voltage detector. This is really ONLY for older kids because it involves ‘playing with electricity’. She was plenty old enough to know not to go anywhere near an outlet, but wanted to know how the power go to one. I grabbed by detector and showed her how it beeped near an outlet and then we traced the wires in the wall with it.
Then I gave it to her and had her guess what would and wouldn’t make it beep. Just putting it near safe things. Would it beep near a chair? How about a cell phone? This cord running up to a lamp? Speakers? The aquarium? A flashlight? Stuffed animals? A toaster? The toaster if I turn it on?
Then I’d have her try to guess why it worked for some things but not others. Granted those detectors can be finicky but she got the hang of it, even down to figuring out that it didn’t beep when she’d hold it next to a plugged in vacuum, but it would if she moved it to a different spot on the vacuum because that’s where the wires must be.
If you have drinking glasses in your kitchen that nest, you can show them how something seemingly solid can change shape with heat. For example, when you take a warm glass out of the dishwasher, then nest it on top of a room temperature glass, when the warm one cools, it will lock onto the other one. By dropping a couple of ice cubes in the “cold” one, eventually the other will release it’s grip. Kind of a simple physics lesson. I asked my kids how to avoid locking glasses, and they were smart and said to put the warm one on the bottom.
Shouldn’t it be the other way around. The warm glass would be bigger, if you put it on top of a cold glass, nothing much will happen when it contracts.
However, if you put a cold glass inside of it, when the warm glass contracts it’ll ‘grab’ the cold glass. The ice cubes would then make the already cold glass even colder thus contracting it further than it is at room temperature. Though you could also run the outside one under warm water.
Also with a straw (must be bendy): Get a ping-pong ball or similarly light spherical object. With the long end of the straw in your mouth, balance the ball on the upturned short end. The challenge is to keep the ball suspended in the air as long as possible by blowing down the straw. The questions are: why does the ball rise into the air? Why does it fall back down? What must be happening when it hovers?
Try to float a paper clip in a bowl of water. You can’t, of course. Now float some tissue paper with the paper clip on top. As the paper dissolves, the clip stays floating due to surface tension.
The first time I saw a vacuum crush an oil can was thrilling. All the teacher did was set a flame inside, a burning strip of paper, and tighten the lid.
You sure about that? For (roughly) every molecule of O2 consumed by the flame, a molecule of CO2 is produced, so there shouldn’t be a change in the number of moles of gas. AIUI, the trick is that the flame heats the air/gas inside the container, making it expand and forcing some of it out before the container gets capped; when the flame goes out, the gas cools, and the pressure inside the container drops.
You can get the same collapsing effect with condensing steam; not seeing what the atmospheric ppO2 has to do with it.
Depending on the age of the kid, you want to minimize the principles involved in the explanation. A microphone is great for explaining electromagnets and how they record sound, but I wouldn’t launch this explanation until a kid is super-solid on sound waves.
Here’s a very simple experiment that kids love.
Wad up a tiny piece of tissue, about the size of a marble. Set an empty plastic liter bottle on its side, and balance the wad of tissue in the mouth of the bottle. Challenge the child to blow the wad of tissue to the back of the bottle.
It looks insanely easy, and all kids are convinced they can do it. But the harder they blow, the faster the wad of tissue pops out of the bottle and flies into their face (to great laughter from everyone).
This is where you start talking about how the bottle isn’t really empty, it has air inside it which takes up room, and when you blow into the bottle, the air in the bottle has to go somewhere, and the only place to go is out of the bottle. The harder you blow into the bottle, the harder the air current coming out of the bottle is.
Even after I explain it, kids always want a second chance. Surely they can defy physics!
A fair number of amusement parks are running school programs using their rides to illustrate different principles. Not quite “every day” but still a good way to get kids excited about science and math.
A microwave oven is a perfect science lesson. Not only is it named after part of the electromagnetic spectrum, but it works by causing polar molecules to spin and thus create friction with each other. And, interestingly, it does not work to heat non-polar molecules. So you can demonstrate that the microwave heats food, which is made almost entirely from polar molecules, but it does not heat the air. (Not directly, that is. Given enough time, hot food will radiate heat to the surrounding air.) Also, there are certain types of plastic dishes that don’t heat up very much in the microwave, because they’re mostly made of non-polar molecules.