Potato Clock

A potato clock runs by converting chemical energy into electrical energy, which is then used to power a clock. The potatoes, in combination with zinc and copper strips (which act as electrodes), act as a battery. Most people aren't aware that this is possible, which is what makes it so interesting.

Check out a video of a potato clock:

 

The energy comes from the chemical change in the zinc when it dissolves inside the mild phosphoric acid content of the potato. The energy does not come from the potato itself. What happens is that the zinc is oxidized inside the potato, exchanging some of its electrons with the potato acid in order to reach a lower energy state, and the energy released provides the electrical power.

Let's imagine first that we have one potato and the zinc and copper strips are inserted into this potato, with a wire connecting the two strips. This potato battery works as follows:

1) The zinc atoms in contact with the potato dissolve in the presence of the acid. This causes some electrons to separate from the zinc atoms. As a result of this, positively charged zinc ions, and negatively charged electrons, are produced.

2) The electrons produced in the above reaction travel out through the zinc, through the wire, and into the copper strip also inserted in the potato. They do this because they are attracted to the positive hydrogen ions in the potato, located on the copper side (these hydrogen ions are there due to the acid content of the potato). Since the electrons cannot pass through the potato itself, they pass through the wire joining the zinc and copper strips. These electrons then combine with these positive hydrogen ions (on the copper side) and produce hydrogen gas, which then bubbles away.

Note that the above chemical reaction happens spontaneously. It is self-driven. The electrons are forced to travel an external path, and if this external path is connected to an electrical device, such as a clock, it powers the device.

Two potatoes can be connected together in order to double the voltage, the same way you join two batteries together to double the voltage. This voltage is sufficient to power the potato clock.


Source : http://www.real-world-physics-problems.com/potato-clock.html

How does rain happen?

Quick Answer

Rain occurs through the process of coalescence, where a mass of water droplets gathers around cloud condensation nuclei to saturate the atmosphere and allow condensation and precipitation to take place. This process is driven by three primary lifting mechanisms that cause the upward movement of air.
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How do Rainbows form ?

Rainbows

by
Lois Polakoff

This lesson was created as a part of the SMART website and is hosted by the Illinois Institute of Technology

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     Have you ever seen a rainbow?  Why do you think rainbows may appear after it rains?  Let us get a piece of glass and hold it up to the sun and try to make a ray of light separate into the seven colors of the rainbow, which is called a spectrum.  In this lesson, we will answer the following questions.  
                                     1.  How and why can a prism split white light into seven colors?.
                                     2.  Name the seven colors of the rainbow.
                                     3.  Explain how the rainbow in the picture above was formed.
     A prism separates white light into a group of  seven colors called a spectrum.  These seven colors are always in the same order.  The colors of the spectrum are red, orange, yellow, green, blue, indigo, and violet.  You can make up a name by using the first letter of each color to form a person's name.  ROY G BIV  Light can be reflected and bent.  When light passes into the prism glass it slows down and it bends.  The color red is not as bent the same way  as  the color violet is bent.   When the colors come out of the prism, each color is bent in a different way and in a different quantity.  People hang prisms from fancy lights in their homes or from windows that the sun shines through  in their homes in order to fill their rooms with rainbows.  
 .  For more information about rainbows see http://eo.ucar.edu/rainbows/

     After it rains, there are lots and lots of water droplets in the air, around us.  When the sun comes out, white light will strike all the drops of water.  Each and every water drop of the millions and millions of water droplets acts just like a prism in that it separates the single strand of white light into seven colors.  Sunlight enters each and every drop of water and the colors are given out as if the drop of water was a prism.  This bending and reflecting happens at the same time in all the droplets of water and that is what forms the colors of the rainbow that you see after it rains.  
     A scientist who did split light by putting a glass prism in a narrow beam of sunlight, actually saw a light that was broken into seven colors by a prism and his name is Isaac Newton.   These are important facts to know in regards to prisms.  Prisms can separate white light into a group of colors called the spectrum.  The spectrum is made of red, orange, yellow, green, blue, indigo, and violet.  Rainbows are very special displays of all the seven colors of light in the spectrum.  Since each raindrop bends and reflects sunlight just like a prism does, sometimes you can see a rainbow just after a rain shower just like the picture at the beginning of this project.
Answer these questions in complete sentences to see if you have learned about rainbows.
1.  Draw a diagram to show what a prism does to white light.
2.  Name all of the colors, in order, which can be found in a rainbow.
3.  Why do raindrops, droplets of water, split white light into colors just like a prism?
4.   What do you think would happen if you placed a prism in front of a spectrum of colors?
     You can make your own rainbow-one that works exactly like one you might see in the sky.  On a bright, sunny day, take a garden hose and use your finger or a nozzle to spray a fine mist up into the air.  You will see a rainbow form in the water droplets as they fall from the fine mist up in the air.
     Rainbows have no end, because they are circles.  You can see the complete circle of a rainbow from an airplane.  There is a reason why you can't see the end of a rainbow from the ground.  For you to see a rainbow, raindrops have to be falling somewhere in front of you, and the sun has to be somewhere behind you.  That way the raindrops can reflect the light from the sun back to your eyes.  You see that light as the colors of the rainbow because light from the sun is made up of all possible colors.  Sunlight gets separated into those colors when it hits the raindrops. 
     If you try to walk to the end of the rainbow, the rainbow will keep moving with you.  The droplets are still in front of you, and the sun is still behind you, so you can never get to the end!     
Here is a great activity that you can try at home to see what white light is made of.
     Get a flashlight, a mirror, a very large bowl of water, and some crayons.
     Put the mirror in the very large bowl of water and shine the flashlight at the mirror.  Move the flashlight from side to side and up and down until you can see the reflection of colors on the ceiling or the walls.  Draw a picture of what you have seen on the ceiling or the walls.  Ask yourself these questions about what happened to the white light from the flashlight and what colors make up white light.  You can see all this from this activity if you do this activity correctly.
For more information on rainbows go to http://www.deltatech.com/rv/rainbows.html
See Poem about Rainbowswith picture
See SunsetRainbows
See RainbowPictures 

Source: http://mypages.iit.edu/~smart/polaloi/lesson2.htm

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How Do You Explain Thunderstorms To Your Kid? Ask A Lightning Physicist

Your kid has endless questions about the endless wonders of the natural world, and while you have an arsenal of apps to help you, you don’t have an army of real-life professors at your disposal — until now. To help you form a coherent answer when your kid asks what’s making those clouds so dark, here’s lightning physicist Joseph Dwyer to break thunder and lightning down into child-sized morsels. Dwyer has authored more than 60 academic papers on the topic and has been featured on PBS, Discovery, and the BBC, but his real credentials lie in the 12 years he spent chasing sky-born kilowattage in Florida without getting electrocuted even once.

YOUR KID’S QUESTIONS

Where does lightning come from?
Up in the clouds, there all sorts of little bits of rain and snow bouncing around. When those pieces bump into each other, they develop an electric charge, which is just like when you drag your feet across the carpet and get a shock, only way more powerful. Most lightning just shoots around in the cloud and we usually don’t even notice it, but every now and then some leaks out and shoots down to the ground. When that happens, the bright thing you see is only as wide as your finger.



Why is it so loud?
When lightning shoots toward the ground, it looks like it’s happening all at once but it’s actually moving really fast – about 60 miles per second. When you’re in the car, you might go 60 miles in an hour, so lightning is that much faster than a car. As the lightning shoots through the air, it heats that air up because lightning is hotter than the sun. When air gets that hot, that fast, it explodes, which is why you hear thunder after you see lightning.

Why is the thunder always after the lightning?
Because thunder is a sound, and sound is a slow poke. Lightning is so bright that you can see it for miles and miles, but thunder can’t always go that far. So, sometimes you see lightning and don’t even hear it, which means it’s pretty far away.

Remember that time we went to Florida, and there was lightning the whole time?
Florida is the lightning capital of the country, because it’s surrounded by warm water and the air has lots of water in it. The winds blow from all around, which pushes all that wet air up into the clouds. Wet air is like a battery for a thunderstorm – it fills the clouds up with all those bits of rain and snow that start bumping into each other and that makes more lightning.

Source : https://www.fatherly.com/activities/how-do-you-explain-thunderstorms-to-your-kid-ask-a-lightning-physicist/

Do Hurricanes have Lightning and Thunder?