 # ELECTRICITY Static Electricity Static electricity is when a charge is built up on an object. The charges do not move. This is usually caused by friction.

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ELECTRICITY

Static Electricity Static electricity is when a charge is built up on an object. The charges do not move. This is usually caused by friction. Examples: feet rubbing against the carpet, combing hair, rubbing a plastic strip with a cloth.

Static Electricity Static electricity cannot hurt. Static electricity does not supply any useful energy.

There are 3 types of charges. Positive Negative Neutral – This means that there is no net charge on the object. There are equal numbers of + and – charges. Opposite charges will attract. Like charges will repel. Neutrally charged objects are attracted by both + & -. This is a very strong force.

Conductors and Insulators A conductor is a substance that allows current to flow through it. Examples: copper & most other metals, graphite, the human body An insulator is a substance that does not allow current to pass through it easily. Examples: plastic, rubber, glass, wood.

Current Electricity Current is when the charges are moving. The movement allows them to do work for us. Examples: lightning, a “shock” from a door knob, current in a wire

Current Current can cause pain and/or be fatal. Care is required. Current also supplies a great deal of useful energy.

Characteristics of Current

Voltage The amount of energy carried by the electrons moving through the circuit. Measured in volts (v) 1 volt = 1 joule per coulomb of charge The voltage is set by the energy source. Example: a 1.5 volt battery or a 110 volt wall socket

Voltage (Potential Difference) Example: What happens when a hot object touches a cold object? Same with electricity  Object with more electrons has a higher potential energy and wants to move to an area with less electrons. Does not depend on number of electrons flowing but the energy levels at two different points.

Current The flow of electrons through a conductor. Measured in amperes (amps) 1 amp = 1 coulomb per second Set by the appliance.

Resistance The tendency of a material to resist the flow of charges. Measured in ohms (  ) The filament in a light bulb has a high resistance. This is why it gets so hot and it glows.

Circuits A closed path that electrons can flow through. Electrons will flow as long as there is a potential difference and the circuit is unbroken. There are two types of circuits: 1. Series 2. Parallel.

Series Circuits In a series circuit all the current must flow through every appliance in the circuit. If one of the appliances goes out, they all go out. Notice that the energy seems to run out.

Series Circuit

Parallel Circuit In a parallel circuit the current flow splits up and goes to different parts of the circuit. If one bulb or appliance goes out, the rest stay on. All bulbs are equally bright.

Parallel Circuit

Schematic Diagrams Series Circuit Parallel Circuit

Direct Current (DC) & Alternating Current (AC)

Direct Current Direct current is when the electrical current moves in one direction all the time. Examples: batteries

Alternating Current Alternating current is when the direction of the flow of current changes 60 times per second. It can be carried long distances from power plants Example: wall sockets

Power The amount of energy used in a period of time; P = energy / time For electricity: Power = voltage x current (P = v x i) Units: watts or kilowatts (1000 watts)

Energy The ability to do work or cause change. For electricity: Energy = voltage x current x time (EE = v x i x t) or (EE = P x t) Units: joules or kilowatt-hours

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