FAQs
How does a battery work?
You will find batteries wherever you go — in your cars, our PCs, laptops, portable MP3 players and cell phones. A battery is essentially a can full of chemicals that produce electrons. Chemical reactions that produce electrons are called electrochemical reactions. Batteries are devices that produce electricity by changing chemical energy into electrical energy.
If you look at any battery, you’ll notice that it has two terminals. One terminal is marked (+), or positive, while the other is marked (-), or negative. In an AA, C or D cell (normal flashlight battery), the ends of the battery are the terminals. Batteries are produced in a ‘Dry Cell’ (paste form), such as those of torch batteries, and ‘Wet Cell’ (liquid form), such as those used in automobiles.Electrons collect on the negative terminal of the battery. If you connect a wire between the negative and positive terminals, the electrons will flow from the negative to the positive terminal as fast as they can. Normally, you connect a load to the battery using the wire. The load could be in the form of a lamp (light bulb) or an electronic circuit, like a radio.How to make battery with a potato?
The chemical reaction that takes place between the two different metal strips and the acid generates electricity. Follow the instructions below to make a potato-powered light bulb.
What you will need:
- A large potato or two small potatoes
- Two coins
- Two zinc-plated nails
- Three pieces of copper wire
- A very small light bulb or LED light
What you need to do:
- Cut the potatoes in half (if using a large potato), then cut a small slit into each half, large enough to slide a coin inside.
- Wrap some copper wire around each coin three times. Use a new wire each time, and not the same wire.
- Stick the coins in the slits you cut into the potatoes.
- Wrap some of the third copper wire around one of the zinc-plated nails and stick the nail into one of the potato halves.
- Take the wire connected to the coin in one of the potatoes with the nail and wrap some of it around the second nail. Stick that second nail into the other potato.
- As soon as you connect the ends of the copper wires to the light bulb or LED it should light up.
What did George Leclanchè invent?
Georges Leclanché invented the Leclanché cell, one of the first modern electrical batteries and the forerunner of the modern dry cell battery. Leclanche's original cell was made out of an absorbent pot. Crushed manganese dioxide with a little cardon mixed in, was used to create the positive electrode.
The negative pole was made of a zinc rod. The cathode - (where the electrons enter an electrical device) was packed into the pot, and a carbon rod was inserted to act as the current collector. The anode + or zinc rod (where the electrons leave a device) and the pot were then placed in an ammonium chloride solution. The liquid acted as the electrolyte, seeping through the absorbent cup and making contact with the cathode material.
The Leclanché cell, which was a heavy battery and not very durable, was gradually improved over time. J.A Thiebaut was the first person to patent the idea of capturing both the negative electrode and absorbent pot into a zinc cup in 1881.
What did Alesandro Volta invent?
Alessandro Volta was an Italian physicist and a pioneer in the study of electricity. He invented the electroscope which is an instrument used to detect small amounts of electricity. Alessandro is best known for inventing a "cell” – a chemical device that can produce a constant flow of electricity.
In 1800, Volta developed a battery which is called a "voltaic pile”. This was made by placing pieces of zinc on top of pieces of copper and separating them by placing strips of cloth soaked in either acid or salt solution between the zinc and copper.
Batteries similar to the voltic pile today are EVEREADY’s PM9 / PP9 (9 Volt) dry cell. We use these kind of batteries in small portable radios and LED desk lamps.
Volta received many honours during his life and is still remembered for his achievements. The force that moves an electric current is called "voltage”, and is measured in units called "volts”, after Volta.
How to make a voltaic pile
You can make a "voltaic pile” using several small copper and zinc coins. (Or, instead of the zinc coins, you can use pieces of zinc.)
The steps:
- Dissolve as much salt as you can into the hot water. Cut the paper towel into pieces and place the in the salt water solution.
- Strip the ends of the insulated copper wires. Tape the end of one wire to the side of a coin. Tape the other end of the other wire to a zinc washer (or a nickel). Place these wires on the top and bottom of your Voltaic stack. It does not matter which wire goes on which end as long as you keep the wires on the outside of the stack.
- Stack the coins and paper towels in alternating layers, for example: copper-zinc-washer-paper towel-copper-zinc-washer-paper-towel and so on. Start with one of your taped coins or a zinc washer and end with the other. You may sprinkle some of the water over the paper towel pieces before stacking them to make sure that they do not dry out
- Connect the free ends of the wires to the leads of the light. If it does not light, check your device to make sure everything is in place correctly. More coins may be added to make the device stronger.
- Use the volt meter and set it on Direct Current voltage to measure how much electricity is being produced by the voltaic pile. You will feel a slight tingling sensation, showing that a small amount of electricity is being generated by the pile.
What is the significance of volts, ohms and amps?
There has to be some "driving force” that makes electrons flow in a conductor. But what is this force and where does it come from? As a simple example, think of a piece of glass that gets rubbed with silk. The glass loses some of its electrons and so becomes positively charged. The silk gained extra electrons and became negatively charged. The difference between the two charges is called the potential difference. This is the "driving force” that was mentioned earlier.If a conductor, such as a piece of wire, was joined to the glass and the silk, electrons would flow back through the wire. The difference in charge would disappear. There would be no potential difference or driving force any more.The potential difference between two ends of a conductor can be measured. Another name for "potential difference is "VOLTAGE”, and the unit by which it is measured is Volts.The larger the voltage, the larger the current in a conductor will be. Doubling the voltage doubles the current in the conductor, and halving the voltage halves the current. A current is measured in units called amperes which are usually shortened to Amps. This describes how much electricity passes through a given point in a conductor per second.There is a relationship between resistance and electric current. The most famous electric law, the "Ohm’s Law” illustrates that a current is halved out, when a wire twice the resistance is used, or doubled when a wire of half the resistance is used.Ohm’s Law states that the current flowing through a conductor is directly proportional to the voltage, and inversely proportional to its resistance. This law is written as an equationVoltage________ = CurrentResistanceResistance is measured in a unit called Ohm, named after George Ohm. Ohm’s Law written in units is:Volts_____ = AmperesOhmsHow to prove with an experiment that like charges repel and unlike charges attract.
In the following experiment you will use balloons and a woollen cloth to prove one of the most important laws: Like charges repel and unlike charges attract.
In 1733 Charles Dufay, a French Scientist, discovered that there were two kinds of electric charges – positive and negative .
What you need to do:
- Rub two inflated balloons with a woollen cloth, and hold the balloons together closely. They will try to spring apart.
- Rub two pieces of nylon on a sheet of paper and then hold them together closely. Again, they will try to spring apart.
- Now hold one balloon and one piece of nylon together closely. This time, the nylon clings to the balloon.
This is what has happened:
- The two balloons took electrons from the woollen cloth and so gained a negative charge.
- The two pieces of nylon lost electrons to the sheet of paper, and so gained a positive charge.
- The two negative charges (on the balloon) tried to push each other away. The two positive charges (on the piece of nylon) also tried to push each other away. But the unlike charges (the balloon and the nylon) tried to move closer together. This is similar to a magnet.
You will see the importance of this law when we examine electric currents and how electric currents are produced. The word "static” means "at rest”, and static electricity are electric charges which are at rest in objects. If we can make these charges move in some way, we will be producing an electric current.
