Physics > Battery > How Batteries Make Electricity

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Grade Category: Elementary

Subject Category: Physics

Sub Category: Battery

Battery Science Projects...
How Batteries Make Electricity

Before you do some battery science projects lets find out how they work. Chemical reactions inside a battery create a large number of free electrons. The flow of these electrons is the current that powers everything from flashlights to cameras to toys.

      Parts of a battery

Cathode-the positive terminal
Anode- the negative terminal
Electrolyte- the chemicals in the battery that produce the free electrons


Dry Cell Battery

Dry Cell Battery

The chemical reaction between the electrolyte and the zinc cannister produces a surplus of electrons at the anode. The cathode has far fewer electrons thus creating a potential difference between the two electrodes. The electrons want to equalize this difference by moving toward the lower build up at the cathode.

The electrolyte though prevents the electrons from moving to the cathode. When a conducter such as a wire is placed across the electrodes then the electrons can move to the cathode. This flow is called electricity or electric current. This current flow of electrons is what powers battery operated devices such as flashlights and all types of electronics kits and devices.

When you start doing battery science projects it will be important to know how batteries work and how to measure the electricity they produce. By learning a few simple principles you will be prepared for some really interesting science fair projects.

Measuring Electricity In Battery Science Projects


We explained that the difference in the amount of electrons at each electrode is what causes the current of electricity to flow. But how do we measure how big that difference is? We use a unit of measure called the volt to describe the potential difference between the two masses of electrons. You will see this listed on all batteries. A common flashlight battery is 1.5 volts. Voltage is the driving force that makes the current flow


The next thing we need to measure is the amount of current that flows through a conductor to a device. This is the quanity of electrons that are moving through a wire or conductor of electricity. This amount of current is measured in amperage. Also called amps for short. For most of the battery science projects you will perform, the current or amps will be small. The current flow depends on the device the batteries are powering. Some pull a very small amount while others pull or use more. So current will always be measured with a load connected to the battery. For a lot of small batteries this will be measured in milliamps or thousandths of an amp.


The power or amount of work a battery is capable of doing is measured in watts. To get the power we simply multiply the voltage times the amperage. The formula is P=I*V where P is in watts, I is the current in amps, and V is the voltage in volts. The power or watts is dependent on the device connected to the battery, just as the current draw is. Some devices will pull a small amount of power and others much more. But this is how power is measured for any particular device.


All wires, conductors, and elctrical devices have some resistance to the flow of electric current. This resistance is measured in ohms or milliohms which is a thousandth of an ohm. The resistance limits how much current can flow through a device or conductor. Its one of the factors that determines how many watts a device will pull. The lower the resistance the more amps and watts it will pull. The higher the resistance the fewer amps and watts it will pull.



How To Make A Potato Battery

This experiment shows you how to make a potato battery and measure the voltage it produces. The current and the voltage produced will be small but it demonstrates how batteries work.

Potato Battery Experiment

Materials needed:

1.One large potato

2.A voltmeter to measure voltage

3.A glavanized nail. A four penny or larger size will work

4.Two inch long piece of single strand copper wire. Either 12 or 14 gauge

4.Piece of sandpaper or steel wool

potato battery


a.Scuff the nail and copper wire with the sandpaper or steel wool until its shiny

b.Push the nail and piece of wire into the flat side of the potato about and inch keeping them an inch or more apart. Make sure they don't touch.

c.Set the voltmeter on its lowest whole number DC voltage. Its 2 on my meter.

d.Plug the red lead of the voltmeter into the +voltage slot. Plug the black lead into the -negative slot(also called common)

e.The nail will be the negative or cathode of the potato battery and the copper wire will be the plus or anode of the battery

f.Turn on the voltmeter and touch the red positive lead to the copper wire and the black negative lead to the nail

My potato battery produced 0.88 volts. The current from this battery will be too small to light a bulb or power an appliance.