History of Electricity

Electricity Definition Useful energy, resulting from the existence of charged particles i. dynamic, as a current ii. static, as a buildup of charge

William Gilbert Credited with naming electricity in about 1600 An English astronomer and physician Also known as the father of electrical engineering

Benjamin Franklin Determined that electricity is created through a relation between positive and negative charges Experiments with a kite and wet string during thunderstorms

B. Coined terms used today when discussing electricity: battery, charge, conductor, plus, minus, positively, negatively, condenser

Electric Charge I. Matter is made of 3 types of particles: Positively charged protons, not charged neutrons, and negatively charged electrons. If the of protons and electrons are equal, a molecule will have no charge.

B. If an atom gains or loses electrons, it can become positively charged (more protons) or negatively charged (more electrons). C. Charged particles can have an effect on each other, creating an electric force in a certain area, called an electric field.

D. Oppositely charged particles attract each other while particles with the same charge repel each other. E. Conductive materials easily share electrons, allowing electrons to be passed along in a “current”

Static Electricity Definition Electrical charge held by a material i. insulating materials can become electrically charged once friction is applied (they are rubbed) ii. charge does not dissipate because there is no conductor.

B. Examples i. being in socks and scuffing your feet on the carpet, then touching someone and giving them a “shock” ii. pulling a sweater/sweatshirt over your head and having your hair then cling to your face

C. In the dark, if the “shock” is big enough, you can see a little “lightning bolt” jumping between you and the object you touch

Lightning Definition Static electricity built up when falling water and rising ice crystals rub together within clouds i. positive charge is at top of clouds, negative at bottom. Charge of ground beneath cloud is positive

ii. A “leader stroke” flashes from cloud, finding an outlet for its negative charge on the positively charged ground iii. Lightning follows, flowing from cloud to ground in a “return stroke” iv. Air heat quickly and expands, creating the noise of thunder

Electric Potential Definition The potential that a charged particle has to influence another. i. dependant on charge, and distance from the other object. II. Measured in Volts, or voltage

Batteries Definition A store of chemical energy that can be converted to electrical energy i. Most common type - dry cell battery ii. Less common - wet cell battery

II. Dry Cell Battery Contains a paste, an electrolyte, which contains charged particles that are able to move. Chemical reactions within the battery separate the charges, positive to one end and negative to the other.

i. The positive end has a steel cap. It sticks upward slightly. ii. The negative end simply is the zinc battery cover. It appears flat. C. Produce an electrical current that moves in one single direction, known as the direct current (DC).

III. Types Primary cells: are dry cells that cannot be recharged. When the chemicals in the electrolyte run out, the battery cannot be used any longer. Secondary cells: are batteries that can be recharged-are known as accumulators.

i. A car battery is a secondary cell, an accumulator. C. Solar cell: converts energy from the Sun into electricity, making electrons move and creating a difference in potential between two layers of silicon. i. calculators

IV. Invention of the Battery Franklin in 1749: Coined the term “battery” when he experimented with electrical current by creating a “battery” using plates of glass coated with metal

B. Volta in 1800: Created piles of copper and zinc discs separated by cloth or cardboard soaked in saltwater (like today’s electrolyte) to produce a stable, though weak current of electricity.

Electric Current Definition A flow of electric charge. It is caused by the sharing of electrons between atoms.

B. Measured as the rate at which charge passes by a certain point on an electric circuit i. Movement is happening within an electrical cord.

C. Example: i. copper wires, which are conductors, allow the electrons to move through them, from high (negative) concentration, to low (positive) concentration. ii. wires are encased in an insulative plastic or rubber tube so that the electrons will flow along the correct path.

II. Types of materials Conductors: those substances through which current can flow. Insulators: those substances through which current cannot flow.

III. Measurement of current Measured in amps. Current = charge ÷ time

Electric Circuit Definition The unbroken pathway through which an electric current flows meaning: a complete circular electric link

II. How it works The power source has two ends, two poles/terminals, with opposite charges (+) and (-), e.g. a battery. The poles indicate the beginning point and end point of the circuit. Elements (bulbs) can be added to circuits

III. Types of circuits Series Circuit: The current passes through elements one after the other, like a chain reaction. If part “a” does not work, then neither will any parts that come after “a.” The current is cut off at the “broken” part.

B. Parallel Circuit: Contains more than one path for the current to travel. If one part of the circuit is “broken,” the current can take the other route, like a detour.

Resistance Definition The ability of a substance to restrict the flow of electric current i. Anything that makes it more difficult for an electric current to be conducted is known as a resistor

ii. Each element of a circuit has a certain amount of resistance, reducing the strength of the current flowing through the circuit at any given time iii. This resistance converts some of the electrical energy into either heat and/or light.

II. Measurement Ohms, named after Georg Ohm, a physicist from the 19th century Symbol is the Greek letter omega: Ω Ohm’s Law: The circuit's current will be stronger when the resistance is less or the voltage is higher.

III. Resistors Electronic components which reduce the flow of current through a circuit. They exist to protect elements in the circuit. (their resistance is differentiated by color)

Each component in a circuit has a different function Components Each component in a circuit has a different function

Variable resistor, also called a rheostat: Adjustable so that the amount of resistance given is changeable. i. volume control on a radio

2. Thermistor: Heat sensitive resistors whose resistance falls as temperature rises i. used in some fire alarms

3. Diodes: Allow current to flow through in one direction only i. Light-emitting diode (LED) glows when current flows through

4. Transistors: Electronic switches consisting of three “legs:” the base, collector, and emitter i. when a small current flows through the base, the transistor allows a larger current to flow between collector and emitter ii. without a current to the base, it is off

5. Capacitors: Store up electrical energy and release it when and as needed i. televisions use them to build up and store high voltages to allow use of the device

6. Transformers: Creates an electrical current in a closed circuit that has no power source by proximity to a circuit that does have a power source.