

The concept of electricity is both familiar and mysterious. We all know what electricity is, or at least have a rough idea, based on practical experience. In particular, consider these points:

  • We are very familiar with the electricity that flows through wires. That electricity comes from power plants that burn coal, catch the wind, or harness nuclear reactions.

    It travels from the power plants to our houses in big cables hung high in the air or buried in the ground. Once it gets to our houses, it travels through wires through the walls until it gets to electrical outlets. From there, we plug in power cords to get the electricity into the electrical devices we depend on every day.

  • We know that electricity isn't free.

  • We know that electricity can be stored in batteries. When the batteries die, all their electricity is gone.

  • We know that some kinds of batteries are rechargeable, which means that when they've been drained of all their electricity, more electricity can be put back into them by plugging them into a charger, which transfers electricity from an electrical outlet into the battery.

  • We know that electricity can be measured in volts. Household electricity is 120 volts (abbreviated 120 V). Flashlight batteries are 1.5 volts. Car batteries are 12 volts.

  • We also know that electricity can be measured in watts. Incandescent light bulbs are typically 60, 75, or 100 watts. Compact fluorescent lights (CFLs) have somewhat smaller wattage ratings. Microwave ovens and hair dryers are 1,000 or 1,200 watts.

  • We also may know that there's a third way to measure electricity, called amps. A typical household electrical outlet is 15 amps (abbreviated 15 A).

  • And finally, we know that electricity can be very dangerous.

But, what is electricity really? Let’s start with three very basic concepts of electricity: namely, electric charge, electric current, and electric circuit.

  • Electric charge refers to a fundamental property of matter that even physicists don't totally understand. Suffice it to say that two of the tiny particles that make up atoms — protons and electrons — are the bearers of electric charge. There are two types of charge: positive and negative. Protons have positive charge, electrons have negative charge.






    All circuits must create a closed loop that provides a complete path from the source of voltage (in this case, the battery) through the various components that make up the circuit (in this case, the lamp) and back to the source (again, the battery).