Electrical energy is a major part of modern day life, but is so often misunderstood. We’ve all sat during a thunderstorm and wondered at the deadly power of lightning. We all know not to touch sockets with wet hands, but do we understand why our hands should be dry? Electricity controls many major functions of our bodies, especially in the brain and nervous system, and is also an extremely versatile resource used in homes and businesses all over the world. The following activities will help students understand the foundation of electrical circuits and how electricity affects our lives every day.
The nature of electricity has baffled scientists for millennia and was only really understood in the last 200 years. The Ancient Greeks first noted the phenomenon of grass seeds sticking to amber (fossilized tree sap) after the amber was rubbed with animal fur. This is something we would later discover as static electricity. The term electricity comes from the Latin word for amber, electrum and was first used by Sir Thomas Browne in the 1600s after William Gilbert’s studies into the attractive properties of amber where he used the term "electricus".
In the late 19th century, the first public electricity network was made in Godalming, England. A Siemens generator was connected to a local water mill and wires ran through the town to connect various lights. Now we live in a new age where we cannot imagine life without electricity. And in this age, there are limits being put on our resources and scientists are looking for newer, greener, and more inventive ways to generate electricity.
A battery connected to a bulb with two wires is the simplest of electrical systems we use to start teaching our students. The battery provides a potential difference that makes the charge in the wires move around the circuit. When the charge flows, we call it an electric current. In order for current to flow, we need something to make the charge move, like a battery, and a complete path for the charges to flow around. If the electric circuit is not complete, an open circuit, the current won’t flow, and thus the bulb will not light up.
The three major variables in elementary circuits are current, voltage (potential difference), and resistance. This is summarized by Ohm’s law: voltage = current x resistance. Voltage is measured in volts, current in Amps and resistance in Ohms. You can measure current using an ammeter that is placed in series in a circuit. To measure voltage, you need to connect a voltmeter in parallel in the circuit.
If we increase the potential difference, by adding more batteries for example, then the current flowing in the circuit will also increase. Resistance is a measure of how difficult it is for the current to flow in a circuit. If we add more bulbs, the total resistance in a circuit increases. If we increase the resistance, it is harder to for electrons to move, so the current decreases, and the bulbs will be dimmer or flicker.