Electricity Electric Charge Positive and Negative Charge Atoms

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Electricity

Electricity

Electric Charge Positive and Negative Charge • Atoms – Protons (+) – Inside nucleus

Electric Charge Positive and Negative Charge • Atoms – Protons (+) – Inside nucleus – Neutron (0) – Inside nucleus – Electron (-) – Outside Nucleus • Static Electricity – excess electric charge • Law of conservation of charge – charge can be transferred but can not be created of destroyed

Electric Charge Positive and Negative Charge • Opposite charges attract • Like charges repel

Electric Charge Positive and Negative Charge • Opposite charges attract • Like charges repel • Electric fields surround every electric charge, this exerts a force that causes other electric charges to repel or attract.

Electric Charge Insulator and Conductors • Conductors – Electrons are able to move •

Electric Charge Insulator and Conductors • Conductors – Electrons are able to move • Example – metal is a good conductor • Insulators – Electrons don’t move • Example – plastic, rubber, wood and glass

Electric Charge Charging Objects • 2 material rub together they transfer electrons – One

Electric Charge Charging Objects • 2 material rub together they transfer electrons – One = positive – The other = negative – This is called “charging by contact”

Electric Charge Charging Objects • Charging by induction – rearrangement of electrons on a

Electric Charge Charging Objects • Charging by induction – rearrangement of electrons on a neutral object caused by a nearby object • Lightning – large static discharge • Thunder – hot air in lightning bolt path expands rapidly, producing sound waves • Ground – connecting an object to earth with a good conductor

Detecting an electric charge • Electroscope – detects electric charge – No charge =

Detecting an electric charge • Electroscope – detects electric charge – No charge = straight down – Charge touches rod…both ends negatively charged = repel

Current and Voltage Difference • Electric Current – net movement of electric charges in

Current and Voltage Difference • Electric Current – net movement of electric charges in a single direction. – Electric Current – Measure in Amps • 1 amp = 6, 250 million billion electrons flowing past a point every second

Current and Voltage Difference • Voltage Difference – force that causes electric charge to

Current and Voltage Difference • Voltage Difference – force that causes electric charge to flow – Measured in volts

Current and Voltage difference • Circuit – closed path that an electric current follows.

Current and Voltage difference • Circuit – closed path that an electric current follows. – If circuit is broken (open) current will not flow.

Batteries • Purpose – provides the voltage difference that is needed to keep electric

Batteries • Purpose – provides the voltage difference that is needed to keep electric current flowing

Batteries • Dry Cell – Chemical reactions in the paste transfer electron to the

Batteries • Dry Cell – Chemical reactions in the paste transfer electron to the zinc container

Batteries • Wet Cell Battery – Made of different metals of metallic compounds in

Batteries • Wet Cell Battery – Made of different metals of metallic compounds in a conducting solution. Contain many wet cells together

Battery • Lead Acid Battery – Series of six wet cells made up of

Battery • Lead Acid Battery – Series of six wet cells made up of lead and lead dioxide plates in a sulfuric acid solution.

Resistance • Resistance – tendency of material to oppose the flow of electrons, changing

Resistance • Resistance – tendency of material to oppose the flow of electrons, changing electrical energy into thermal energy and light

Current in a simple circuit • Contains a source of voltage difference (battery) a

Current in a simple circuit • Contains a source of voltage difference (battery) a device that has resistance (light bulb) and conductors that connect the device to the battery terminals.

Current in a simple circuit • Ohm’s Law – current in a circuit equals

Current in a simple circuit • Ohm’s Law – current in a circuit equals the voltage difference divided by the resistance • I = V/R • Current = voltage difference / resistance – Current – Amps – Voltage Diff – Volts – Resistance - Ohms

Series Circuits • Current has only one loop to flow through – Flash lights

Series Circuits • Current has only one loop to flow through – Flash lights and some holiday lights • Open circuit – when any part of the circuit is disconnected no current flows through the circuit

Parallel Circuits • Contain two or more branches for current to move through •

Parallel Circuits • Contain two or more branches for current to move through • Advantages – when one branch is opened (turn off a light) the current flows through the other branches

Household Circuits • Parallel Circuits • In a house many appliances draw from the

Household Circuits • Parallel Circuits • In a house many appliances draw from the same circuit. More appliances = more heat – Fuse – current becomes too high small piece of metal melts causes a break in the circuit. – Circuit breaker – current gets to high, a small piece of metal bends and opens the circuit, can usually be reset by pushing it back to on position.

Electrical Power • Electrical Power – rate at which electricity is converted into another

Electrical Power • Electrical Power – rate at which electricity is converted into another form of energy – Appliances with electric heating elements (ovens, hair dryers, ovens) use more electrical power that other appliances.

Electrical Power • Calculating electrical power – depends on the coltage difference and current

Electrical Power • Calculating electrical power – depends on the coltage difference and current • Electrical Power = current(Amp) X Volatage diff. (volts) Unit for power = watts KW = 1, 000 watts

Electrical Power • Electrical Energy = k. Wh • k. Wh = electrical power(k.

Electrical Power • Electrical Energy = k. Wh • k. Wh = electrical power(k. W) X Time(hrs)