"Watt's" the Cost? Background Notes

Static Electricity and Charged Particles

• Static electricity is an imbalance between quantities of positive and negative particles already present (charge separation).
• There are two kinds of static charges, positive and negative.
• Like charges repel and unlike charges attract.
• Charges can transfer on contact.
• Induced charges result from an object being near another strongly charged object.
• If a positively charged object approaches a neutral object, the neutral object becomes negatively charged. If a negatively charged object approaches a neutral object, the neutral object becomes positively charged. The induced charge is always opposite that of the charged object.
• Rubbing one material (balloon) on another will result in the loss of some electrons; thus, the rubbing material (balloon) obtains excess electrons, which means that it has a negative charge. The most common materials used to charge objects are wool, cotton cloth, flannel, and hair.

Current Electricity and Circuits

• An electric current is a flowing motion of charged particles.
• Electrical energy moves as wave energy.
• The term current refers to a behavior of electrical charges.
• Currents are the moving electrical charges that are pushed through the wire by electromotive force (voltage).
• Current is a flow of matter, not an energy flow.
• Current electricity is NOT the opposite of static electricity! Current refers to the negative charges within matter being forced to flow through the positive charges.
• Moving electrons (electricity) do not travel very fast. The energy the electrons transfer is what travels very fast -- at the speed of light!
• Electricity can be created from chemical sources.
• In an electric circuit, the path of the electrical charges is circular, while the path of the energy is not. (A battery can send electric energy to a lightbulb, and the bulb can change electrical energy into light. The energy does not flow back to the battery again.)
• When a battery is placed in a simple circuit, the electrical current flows through the battery's liquid electrolyte to complete the circuit; therefore, a battery pushes charges rather than supplies them and is considered a charge pump.
• Within a flashlight circuit, the electrons that are being moved run through the entire circuit. The flashlight batteries are not generating the electrons.
• The resistance the electron experiences is caused by the energy given off in the form of light as it circulates through the lightbulb. This resistance causes the electrons to slow down.

Miscellaneous

• Energy can be measured in joules or ergs.
• The rate of energy flow is measured as joules per second, or power. Watt is a term used to measure the rate of energy flow when it should really be referenced as joules per second (J/sec).