Petrol-powered vehicles are a major source of the gases that cause global warming. Other gases released from vehicle exhausts also cause other problems, such as asthma attacks in children. By changing to electrically powered cars (especially those that are powered from renewable resources), the quality of our environment would improve, especially in our cities. However, the range of electric cars is limited by the need to carry heavy batteries that can store only a fraction of the energy contained in petrol. Also, if the electricity to power the electric car comes from fossil fuels like coal, then pollution is simply moved from the car to the power station.

In this activity, you will investigate how different materials can produce electrical energy by making your own battery.

Electric cars don't have many of the parts that petrol-powered cars do--parts that need continual upkeep at best, and that often fail (e.g., fuel injectors, carburettors, mufflers, distributors, water pumps, etc.). There are no tune-ups or oil changes for electric cars. There is no emission-control system, which is one of the most complex and expensive parts of a car that uses petrol. Most of the components in an electric car are electrical or solid-state, with no moving parts. The overall costs for maintaining an electric car average about 30% of that for petrol-powered cars.

So, if electric vehicles are so great, why don't we see many around? There are several reasons for this, the primary one being the relative efficiency of petrol as a fuel. Petrol is fairly inexpensive to produce; because it's a liquid, it's cheap to store and transport; and it has a very high energy content per unit of weight.

There are developments in electric cars that might eliminate some of the disadvantages. One example is a car fuelled by electrical metal strips laid within the roadbed. Electrical energy is provided from a central source through the metal strip. These electric cars do not require a battery source, only an electric motor.

The electric-vehicle industry continues to grow. However, today, the cost of an electric car is still higher than petrol-powered cars. Many "do-it-yourselfers" are converting their petrol-powered cars to electric cars, thus saving money.

Our dependence on the internal combustion engine is costing us in many ways, especially to the environment in our cities. Electric vehicles can bring us cleaner air and greater energy independence.

Materials

• #6 dry cell
• knife switch OR push button
• compass
• 5 metres of 28-gauge (or finer) insulated wire

1. Wind the insulated wire about 10 times around the compass at the north- and south-pole markings. The compass should be rotated so that the compass needle is also aligned in a north-south direction.
2. Connect the wires in a complete circuit.
3. Use the knife switch or push button to close the circuit only for a moment at a time.

CAUTION: Leaving the circuit closed will result in a short circuit with the wires becoming very hot!

4. Now make your own batteries using household items and test them in the next investigation. Use the "compass" galvanometer to detect an electric current after constructing it in steps 1 through 4.

1. What happened to the compass needle when the circuit was closed?

2. How do you know that the deflection of the compass indicates a current flow? Try showing that a straight wire can also cause the compass to deflect when near a current-carrying wire.

Part II

• lemon
• vinegar
• orange juice
• wire from Part I
• compass from Part I
• copper strip approximately 3/4" wide and 5" long
• zinc strip approximately 3/4" wide and 5" long
• wide-mouth glass jar

1. Carefully squeeze or roll on a hard surface the unpeeled lemon until it feels very soft. Be careful not to break or puncture the skin. Push the copper and zinc strips into the lemon.
2. Wrap the ends of the wires from the compass galvanometer around the metal strips as illustrated. What happened to the compass needle when the circuit was closed? Was the compass needle deflected? What does that indicate?
3. Now repeat the procedure using a jar of vinegar and then a jar of orange juice. Be sure to wash the metal strips with water before testing a new substance.

1. What would happen if you used a non-conducting liquid, such as milk? What needs to be present to cause a current to flow?

2. Look at and identify the parts of a battery. What components in your circuit correspond to these parts?