Electricity Electricity and Voltage Electricity is the flow

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Electricity!

Electricity!

Electricity and Voltage - Electricity is the flow of electrons (-) Charges (-) flow

Electricity and Voltage - Electricity is the flow of electrons (-) Charges (-) flow from HIGH voltage (high – charged) areas to LOW voltage areas • Voltage is like electrical pressure that pushes, pulls charges • Voltage Difference: the push/pull that causes charges to move and is measured in volts (V)

Electricity - electrons moving through a metal wire.

Electricity - electrons moving through a metal wire.

Voltage is Difference in Potential b b Difference in electric potential between two points.

Voltage is Difference in Potential b b Difference in electric potential between two points. Potential difference b/w A and B is 0 A B

Electrical Energy - is the force of moving electrons.

Electrical Energy - is the force of moving electrons.

Electrical Energy Measured in… Voltage Current Resistance

Electrical Energy Measured in… Voltage Current Resistance

Electric Charges Matter is made of atoms, which are made of subatomic particles called…

Electric Charges Matter is made of atoms, which are made of subatomic particles called… b electrons, b protons, and b neutrons. b

Electric Charges b b b Electrons (e‾) have a negative charge. Protons have a

Electric Charges b b b Electrons (e‾) have a negative charge. Protons have a positive charge. Neutrons are neutral - no charge.

Electric Charges b b Electrons can move from one atom to another, but protons

Electric Charges b b Electrons can move from one atom to another, but protons cannot move. When an atom has gained electrons, it has more electrons than protons, and it is negatively charged. When an atom has lost electrons, it has more protons than electrons, and it is positively charged. Rule of Charge: Opposite charges attract, like charges repel.

Electric Charges b b Electrons can move from one atom to another, but protons

Electric Charges b b Electrons can move from one atom to another, but protons cannot move. When an atom has gained electrons, it has more electrons than protons, and it is negatively charged. When an atom has lost electrons, it has more protons than electrons, and it is positively charged. Rule of Charge: Opposite charges attract, like charges repel.

Static (not flowing) Electricity …is when there is an excess of electric charges on

Static (not flowing) Electricity …is when there is an excess of electric charges on an object. a. More e‾ = negative charge b. More protons = + charge 2. Charge is conserved (e‾ move from one object to another).

Static Electricity when a material has an excess or a lack of electrons.

Static Electricity when a material has an excess or a lack of electrons.

Static electricity 1/11/2022 13

Static electricity 1/11/2022 13

Electric Fields Picture how it feels to be outside before a strong thunderstorm. You

Electric Fields Picture how it feels to be outside before a strong thunderstorm. You are, more or less, in an electric field.

Electric Fields An area where the effects of charged particles can be measured -

Electric Fields An area where the effects of charged particles can be measured - + There is an electric field around and between these two charged particles.

Electric Fields - + Electric fields “push or pull” on objects within the field.

Electric Fields - + Electric fields “push or pull” on objects within the field. Those effects vary, depending on…

Electric Fields - + . . . the charge on whatever is put within

Electric Fields - + . . . the charge on whatever is put within the field, and …how close it is to the particles that create the field.

Charge and Force b b Like charges repel each other, and unlike charges attract

Charge and Force b b Like charges repel each other, and unlike charges attract each other. The electric field is strongest when you are closest to the charge. + - charged balloon sticks to +charged area of a wall.

b Electrons can be rubbed off of one object and onto another. The objects

b Electrons can be rubbed off of one object and onto another. The objects then get a static charge. b When neutral objects are rubbed together and charges are rearranged, the objects get unlike charges, and they stick together.

Static electricity 1/11/2022 Girl has lost electrons from her hair. + charges remaining repel

Static electricity 1/11/2022 Girl has lost electrons from her hair. + charges remaining repel each other 20

Lightning! b b During a storm, water and dust particles in clouds are rubbed

Lightning! b b During a storm, water and dust particles in clouds are rubbed together by winds. This friction creates + and – charges in the clouds. - charge + charge - charge

b b When a highly charged cloud is over land, a charged area on

b b When a highly charged cloud is over land, a charged area on the ground is produced. Charges are now separated! Lightning is caused by the discharge (equalization) of these separate static electric charges. + charge - charge + charge - charge

Transferring Electric Charge Contact charging is done when two materials are rubbed together Charging

Transferring Electric Charge Contact charging is done when two materials are rubbed together Charging by induction is done when one charged object induces a charge on another.

Electric Current b Electric current is when electrons flow through a wire or another

Electric Current b Electric current is when electrons flow through a wire or another conductor. b For electricity to flow, you need a closed continuous path, called a circuit. b You also need a difference in charge from one end of the wire to the other that pushes the electrons. This is called potential difference or voltage.

§ Voltage is like the amount of flow there is or could be. §

§ Voltage is like the amount of flow there is or could be. § Voltage causes current. § The symbol for voltage is V. § You need to know this for calculations.

§ Current is like how hard the push is behind the voltage. § Current

§ Current is like how hard the push is behind the voltage. § Current is measured in amperes, or amps. § The symbol for amps is I. § You need to know this for calculations.

The amount of electric charge is measured in coulombs. § 1 coulomb is the

The amount of electric charge is measured in coulombs. § 1 coulomb is the charge carried by 6. 24 x 10^18 electrons § 1 amp is 1 coulomb (6. 24 x 10^18 electrons) per sec.

Resistance or Impedance § Opposition to the flow of electrons in a circuit. §

Resistance or Impedance § Opposition to the flow of electrons in a circuit. § Changes electrical energy into thermal energy and/or light. § Measured in ohms (Ω). Labeled as “R” § You need to know this for calculations. § Conductors have less resistance than insulators.

Electric Current b b Electrochemical cells and thermocouples cause the voltage that makes electrons

Electric Current b b Electrochemical cells and thermocouples cause the voltage that makes electrons flow. There are two kinds of electrochemical cells---wet cells such as a car battery and dry cells like flashlight batteries.

Batteries are electron pumps. a. They provide a voltage difference (potential) to a circuit.

Batteries are electron pumps. a. They provide a voltage difference (potential) to a circuit. b. Types: wet-cells & dry-cells

Two Types of Current: AC and DC b b When the electrons flow in

Two Types of Current: AC and DC b b When the electrons flow in only one direction, this is called direct current. , or DC. Current from batteries is always direct current.

b When electrons first go in one direction, then reverse, then back again, this

b When electrons first go in one direction, then reverse, then back again, this is called alternating current, or AC. b Current from generating plants that powers our homes and businesses is alternating current.

Conductors and Insulators b b b Materials through which electrons can move easily are

Conductors and Insulators b b b Materials through which electrons can move easily are good conductors. Most metals, acids, sea water, tap water are good conductors De. Ionized water does not conduct electricity. No charged particles!

Conductors and Insulators b b b Insulators: electrons can’t move easily through them Wood,

Conductors and Insulators b b b Insulators: electrons can’t move easily through them Wood, ceramic, rubber, glass… Charges can build up on the surface of good insulators, and stays there as a static charge , ex. balloon

Ohm’s Law: V = I R b b Ohm’s Law relates the push behind

Ohm’s Law: V = I R b b Ohm’s Law relates the push behind electric current to the number of electrons flowing and to the resistance to their flow. The rate of electrons flowing through a circuit is called current. The letter I stands for current. Current is measured in Amperes or amps (A). V I R

Ohm’s law: V = IR, So… Voltage Resistance Current = Rearrange the equation as

Ohm’s law: V = IR, So… Voltage Resistance Current = Rearrange the equation as needed. V I R

Types of Circuits b A circuit in which the current must pass through all

Types of Circuits b A circuit in which the current must pass through all of the resistors on only one path is called a series circuit. #1 #3 #2

Types of Circuits b A circuit in which the current can travel through more

Types of Circuits b A circuit in which the current can travel through more than one path is called a parallel circuit. #1 #3 #2

Comparison of series and parallel circuits The same voltage battery Notice the brightness of

Comparison of series and parallel circuits The same voltage battery Notice the brightness of the bulbs

Series Circuit One path Any break & all devices go out Current (amps) is

Series Circuit One path Any break & all devices go out Current (amps) is the same throughout the circuit. Voltage different at each location, but adds-up to source voltage

Parallel Circuit q Multiple paths q A break in one branch & the others

Parallel Circuit q Multiple paths q A break in one branch & the others stay on Voltage (V) same throughout the circuit. Current (I) can vary depending on resistance.

Parallel Circuit Kirchoff’s Law: If current flows into a branch in a circuit ,

Parallel Circuit Kirchoff’s Law: If current flows into a branch in a circuit , the same amount of current has to flow out.

Parallel Circuit Kirchoff’s Law:

Parallel Circuit Kirchoff’s Law:

Series Circuit Calculations (assuming 3 resistors) To calculate resistance (ohms/Ω) for the whole circuit

Series Circuit Calculations (assuming 3 resistors) To calculate resistance (ohms/Ω) for the whole circuit – add them! Rcircuit = R 1 + R 2 + R 3…

Circuit Calculations

Circuit Calculations

Series Circuit Calculations To calculate volts (V) for the circuit Vcircuit = (I •

Series Circuit Calculations To calculate volts (V) for the circuit Vcircuit = (I • R 1) + (I • R 2) + (I • R 3) or, Vcircuit = I • (R 1 + R 2 + R 3) To calculate amps (I) for the circuit since I=V÷R then… ICIRCUIT = V ÷ (R 1 + R 2 + R 3)

Parallel Circuit Calculations (assuming 3 paths) V is the same everywhere in the circuit

Parallel Circuit Calculations (assuming 3 paths) V is the same everywhere in the circuit I varies in each branch. ITOTAL = Sum of the branches I 1 + I 2 + I 3

Parallel Circuit Calculations (assuming 3 paths) since ITOTAL = V ÷ R and I

Parallel Circuit Calculations (assuming 3 paths) since ITOTAL = V ÷ R and I 1 = V ÷ R 1 then V ÷ R = V ÷ R 1 1 + V ÷ R 2 + V ÷ R 3 1 RTOTAL R 1 R 2 R 3

Household Circuits a. Mostly parallel. b. 120 V in the U. S. c. More

Household Circuits a. Mostly parallel. b. 120 V in the U. S. c. More devices plugged in a circuit mean more current pulled. d. More current means more heat in the wiring.

Household Circuits SAFETY More devices plugged in a circuit mean more current. More current

Household Circuits SAFETY More devices plugged in a circuit mean more current. More current means more heat in the wiring. Can create a dangerous situation.

Electrical safety devices a. Fuses - one time use. b. Circuit breakers - can

Electrical safety devices a. Fuses - one time use. b. Circuit breakers - can be reset and reused.

Electric Power and Energy 1. Electrical power is the rate at which electricity is

Electric Power and Energy 1. Electrical power is the rate at which electricity is converted into another form of energy. a. Power = current x voltage b. Unit is the watt or kilowatt (1000 watts).

Electric Power and Energy 2. Electrical energy a. Energy = power x time b.

Electric Power and Energy 2. Electrical energy a. Energy = power x time b. Unit is the kilowatt-hour. (1000 watts for 1 hour) c. This is what we buy from the electric company.

Light Bulbs

Light Bulbs

Incandescent a. Have a tiny filament that resists the flow of electrons. b. The

Incandescent a. Have a tiny filament that resists the flow of electrons. b. The filament gets hot and glows to produce light. c. Very hot and inefficient.

Fluorescent a. Filled with gas and coated with phosphor. b. Electricity excites the gas

Fluorescent a. Filled with gas and coated with phosphor. b. Electricity excites the gas c. making it give off U-V rays.

Fluorescent (cont. ) c. Phosphor coating inside the tube absorbs U-V rays and glows

Fluorescent (cont. ) c. Phosphor coating inside the tube absorbs U-V rays and glows to make light. d. Very cool, efficient, and last a long time.