Electric Charge Electric Charge and Static and Static ElectricityElectricity

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Electric ChargeElectric Charge Electric charge is a property that Electric charge is a property that

causes subatomic particles (protons causes subatomic particles (protons and electrons) to attract or repel each and electrons) to attract or repel each other.other.

There are two types of electric charge:There are two types of electric charge:Positive (proton)Positive (proton)Negative (electron)Negative (electron)

Electric ChargeElectric Charge An atom is neutral with a positive An atom is neutral with a positive

nucleus and is surrounded by a nucleus and is surrounded by a negatively charged cloud of electrons.negatively charged cloud of electrons.

An excess or shortage of electrons An excess or shortage of electrons produces a net electric charge (ion).produces a net electric charge (ion).

The SI unit of electric charge is the The SI unit of electric charge is the coulomb (C)coulomb (C)

Recap of the AtomRecap of the Atom

Electric ForcesElectric Forces Like charges repel, and opposite Like charges repel, and opposite

charges attract.charges attract.

The attraction or repulsion between The attraction or repulsion between electrically charged objects is electrically charged objects is electric force.electric force.

EX: balloon and hairEX: balloon and hair

Electric ForcesElectric Forces The electric force between two objects The electric force between two objects

is directly proportional to the net is directly proportional to the net charge on each object and inversely charge on each object and inversely proportional to the square of the proportional to the square of the distance between them.distance between them.

aka the larger the charge, the larger aka the larger the charge, the larger the electric force. The larger the the electric force. The larger the distance, the smaller the electric force.distance, the smaller the electric force.

Electric ForcesElectric Forces Inside an atom, electric forces are Inside an atom, electric forces are

much stronger than gravitational much stronger than gravitational forces.forces.

Electric FieldsElectric Fields The effect an electric charge has on The effect an electric charge has on

other charges in the space around it other charges in the space around it is the charge’s electric field.is the charge’s electric field.

The strength of an electric field The strength of an electric field depends on the amount of charge depends on the amount of charge that produces the field and on the that produces the field and on the distance from the charge.distance from the charge.

Electric FieldElectric Field The lines representing the field are The lines representing the field are

closer together near the charge, closer together near the charge, where the field is stronger.where the field is stronger.

Field of a Positive and Field of a Positive and Negative ChargeNegative Charge

Static Electricity and Static Electricity and ChargingCharging

Static electricity is the study of the Static electricity is the study of the behavior of electric charges, behavior of electric charges, including how charge is transferred including how charge is transferred between objects.between objects.

Charge can be transferred by Charge can be transferred by friction, contact (conduction), and friction, contact (conduction), and induction.induction.

Static Electricity and Static Electricity and ChargingCharging

The law of conservation of charge The law of conservation of charge states that the total charge is the states that the total charge is the same before and after the transfer same before and after the transfer occurs.occurs.

Charging by FrictionCharging by Friction Rubbing two objects together causes Rubbing two objects together causes

friction, which causes a transfer of friction, which causes a transfer of electrons.electrons.

Charging by ContactCharging by Contact Whenever two objects touch (not Whenever two objects touch (not

rubbed together) and charge is rubbed together) and charge is transferred.transferred.

Charging by InductionCharging by Induction A transfer of charge without contact A transfer of charge without contact

between materials.between materials.

EX: walking across carpet and then EX: walking across carpet and then touching a door knob.touching a door knob.

Static DischargeStatic Discharge Static discharge occurs when a pathway Static discharge occurs when a pathway

through which charges can move forms through which charges can move forms suddenly.suddenly.

Charges will not travel through air from Charges will not travel through air from your hand to the doorknob. The air your hand to the doorknob. The air becomes charges suddenly when the gap becomes charges suddenly when the gap between your finger and the doorknob is between your finger and the doorknob is small. This air provides a path for small. This air provides a path for electrons to flow from your hand to the electrons to flow from your hand to the doorknob.doorknob.

Electric Current Electric Current and Ohm’s Lawand Ohm’s Law

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Electric CurrentElectric Current The continuous flow of electric charge is The continuous flow of electric charge is

an electric current.an electric current.

The SI unit of electric current is the The SI unit of electric current is the ampere (A), or amp, which equals 1 ampere (A), or amp, which equals 1 coulomb per second.coulomb per second.

The two types of current are direct The two types of current are direct current and alternating current.current and alternating current.

Electric CurrentElectric CurrentDirect current (DC) is where charge only Direct current (DC) is where charge only

flows in one direction.flows in one direction.

Alternating current (AC) is a flow of Alternating current (AC) is a flow of electric charge that regularly reverses electric charge that regularly reverses its direction.its direction.

Current is the direction in which Current is the direction in which positive charges flow.positive charges flow.

Direct CurrentDirect Current

Conductors and Conductors and InsulatorsInsulators

An electrical conductor is a material An electrical conductor is a material through which charge can flow easily.through which charge can flow easily.

EX: copper and silverEX: copper and silver

A material through which charge A material through which charge cannot flow easily is called an cannot flow easily is called an electrical insulator.electrical insulator.

EX: wood, plastic, rubber, and airEX: wood, plastic, rubber, and air

ResistanceResistance Resistance (R) is opposition to the Resistance (R) is opposition to the

flow of charges in a material.flow of charges in a material.

The SI unit of resistance is the ohm.The SI unit of resistance is the ohm.

ResistanceResistance A material’s thickness, length, and A material’s thickness, length, and

temperature affect its resistance.temperature affect its resistance.

A superconductor is a material that A superconductor is a material that has almost zero resistance when it is has almost zero resistance when it is cooled to low temperatures.cooled to low temperatures.

VoltageVoltage In order for charge to flow in a In order for charge to flow in a

conducting wire, the wire must be conducting wire, the wire must be connected in a complete loop that connected in a complete loop that includes a source of electrical energy.includes a source of electrical energy.

Potential difference is the difference in Potential difference is the difference in electrical potential energy between two electrical potential energy between two places in an electric field.places in an electric field.

Voltage Voltage Potential difference is also called Potential difference is also called

voltage (V).voltage (V).

Three common voltage sources are Three common voltage sources are batteries, solar cells, and generators.batteries, solar cells, and generators.

A battery is a device that converts A battery is a device that converts chemical energy to electrical energy.chemical energy to electrical energy.

Ohm’s LawOhm’s Law Ohm’s Law states that the voltage (V) in Ohm’s Law states that the voltage (V) in

a circuit equals the product of the a circuit equals the product of the current (I) and the resistance (R):current (I) and the resistance (R):

V = I x RV = I x R

Increasing the voltage increases the Increasing the voltage increases the current. Keeping the same voltage and current. Keeping the same voltage and increasing the resistance decreases the increasing the resistance decreases the current.current.

Ohm’s Law PracticeOhm’s Law Practice What is the voltage if the resistance What is the voltage if the resistance

is 3 ohms and the current is 3 amps?is 3 ohms and the current is 3 amps?

V = I x RV = I x R