SAT VOCAB 3• Attribute (v) to credit, assign (n) a facet or

trait• Permeate (v) to spread throughout, saturate• Transmute (v) to change or alter in form• Reciprocate (v) to give in return

SAT VOCAB 3Over the Thanksgiving break, many get together for a big family dinner. Whatever your family tradition is, the recipes for the different dishes are ___________________ to family members or friends because each recipe comes from a different person. My family always has a grits casserole, a custom that has _________________ now to all the holiday dinners. Some friends have tried to make the dish, but its form has _________________ with each person’s attempt to make it. If we invite friends to our Thanksgiving family dinner, they ______________________ by bringing a dish themselves.

ELECTRICITY

ELECTRIC CHARGES

• Atoms are composed of three main parts:–Proton, p+, positive, located in the nucleus–Neutron, no, neutral, located in the nucleus–Electron, e- , negative, located outside the

nucleus in the electron cloud.• Everything is made of atoms.

ELECTRIC CHARGES

• Protons and electrons have a property called electric charge.

• An atom has equal numbers of positive and negative charges so they cancel each other out.

• Electrons can move from one atom to another atom. This movement is called electric current.

STATIC ELECTRICITY

• Some atoms hold their charges more tightly.

• Latin word “stasis” which means “stays”.

• Static electricity is the temporary building up of charge on an object.

• Protons DON’T move.• Only electrons move.• In static electricity, the charges build

up and stay – they do not flow.

STATIC ELECTRICITY

• When you walk across a carpet, FRICTION causes electrons to move from the carpet to your shoe. This is a build-up of static electricity. You discharge the electricity by touching a conductor.

LAW OF CONSERVATION OF

CHARGE• When an object becomes charged, the electric

charge is neither created nor destroyed – it just came from another object.

• Static electricity is an imbalance in the amounts of positive and negative charges on the surface of an object.

STATIC ELECTRICITY

• Another way to generate static electricity is with a Van de Graaf generator.

• American physicist Robert Jemison Van de Graaf invented the Van de Graaf generator in 1931.

• Van de Graaf generator

STATIC ELECTRICITY

• There are three ways to charge on object:–Friction– Induction–Conduction (contact)

STATIC ELECTRICITY

• Charging by Friction- The charge is

transferred because of rubbing two objects together.

- Example: shoes on a carpet

- Animation

STATIC ELECTRICITY

• Charging by Induction– Involves the charging of one object by another

object WITHOUT direct contact.–Example: balloon and rice cereal/electroscope

STATIC ELECTRICITY

• Charging by Conduction– Involves the DIRECT CONTACT of a charged

object to a neutral object.–Example: Van de Graaf generator

STATIC DISCHARGE• Objects do not hold a static charge forever –

objects tend towards equilibrium – they want to be neutral.

• When electrons move toward this equilibrium – static discharge occurs.– Humidity – water (a polar molecule) vapor in the air

pulls electrons off negatively charged objects, preventing static charges to build up.

– Sparks and Lightning - objects reaching static equilibrium

CONDUCTORS• Allow the easy flow of electricity• loosely bound electrons that are free to move

from atom to atom• Examples: metals like aluminum, gold, copper

and silver .

INSULATORS• Insulators – resists the flow of electrons

–hold more tightly to their valence electrons.

–Examples: plastic, rubber, glass

VOCABULARYElectric field - the electric force per unit charge; it is radially outward from a positive charge and radially in toward a negative point charge.

ELECTRIC CURRENT• The constant flow of electrons.

ELECTRIC CURRENTREMEMBER:• Conductors let electrons move easily.• Insulators do not let electrons move easily.• A SEMICONDUCTOR has conductivity

somewhere between an insulator and a conductor. Devices made of semi-conductors, notably silicon, are essential components of most electronic circuits.

ELECTRIC CURRENTThere are three parts to an electric charge- Voltage- Current- Resistance

VOLTAGE• Voltage - For electrons to flow there must be a

potential difference between two places.• This is called VOLTAGE which is the “push” that

causes electrons to flow.• It is electrical “pressure”.• Charges flow from high voltage to low voltage.• Units: Volts, V

CURRENT• Current - the measure of how many

electrons per second are flowing through the wire is the amperage.

• Units: amps

• The number of electrons flowing per second.

current

Electrical current is like the amount or volume of water flowing through the hose.

There are two types of current:AC – alternating currentDC – direct current

RESISTANCE• Resistance - the tendency for a material to

oppose the flow of electrons.• Different materials have different amounts

of resistance to the flow of electrons.• Unit: ohm, R.

RESISTANCEEXAMPLES: • gold, silver, and copper have low

resistance, which means that current can flow easily through these materials.

• Glass, plastics, and wood have very high resistance, which means that current cannot pass through these materials easily.

• Resistance

RESISTANCE• Thin wires provide more resistance than do thick

wires.• Resistance in wires produces a loss of energy (usually

in the form of heat), so materials with no resistance produce no energy loss when currents pass through them.

• Resistance also depends on temperature, usually increasing as the temperature increases.

•

ELECTRIC CURRENT

OHM’S LAW

• In a material, the current (I) is directly proportional to the voltage (V) and inversely proportional to the resistance.

• Ohm’s LAW

OR OR

ANALOGY

Water in a Hose DC in a Wire Electrical Units

pressure voltage (V) Volts, V

volume current (I) Amps, A

friction resistance (R) Ohms, R

Charge, Current, and Voltage review

PRACTICEWhat is the current produced with a 9-volt battery through a resistance of 100 ohms?

I = ?

R = 100 ohms

V = 9 volts

I = =

= 0.09amps

BATTERIESTWO TYPES:1. Dry Cell – the electrolyte is not really dry; but is a paste.

– Standard AA, C, D type batteries, electrolyte is a paste. The “+” terminal is carbon.

2. Wet Cell – the electrolyte is a liquid (car battery)– In a car battery, the electrolyte is sulfuric acid.

VOCABULARY1. Dry Cell – a type of chemical cell, commonly

used today, in the form of batteries, for many electrical appliances. It uses a paste electrolyte, with only enough moisture to allow current to flow.

2. Wet Cell – An electric battery is a device consisting of two or more electrochemical cells that convert stored chemical energy into electrical energy using a liquid electrolyte

BATTERIESBatteries have three parts.- A cathode (+)- An anode (-)- An electrolyte.

The cathode (positive) and anode (negative) at either end of a traditional battery) are hooked up to an electrical circuit.

BATTERIES• The chemical reactions in the battery causes a build up

of electrons at the anode.

• This results in an electrical difference between the anode and the cathode - an unstable build-up of the electrons.

• The electrons wants to rearrange themselves to get rid of this difference. They do this in a certain way. Electrons repel each other and try to go to a place with fewer electrons.

ELECTRICAL CIRCUIT• They provide a pathway for electrons to

flow.

Four Parts:1. Energy Source2. Load3. Wires4. Switch

ELECTRICAL CIRCUITOPEN CIRCUITS – pathway is broken.

ELECTRICAL CIRCUITCLOSED CIRCUITS – pathway is complete.

SERIES CIRCUIT• Provides only one path for the electrons to

follow.1. A break in the circuit stops the flow of electricity to

all other parts of the circuit.

2. With multiple light bulbs (more resistance) the current reduces and the lights become dimmer.

3. Ammeters should be wired in series.

SERIES CIRCUIT

RULES

1. The same current flows through each part of a series circuit.

2. The total resistance of a series circuit is equal to the sum of individual resistances.

a. What is the total voltage across the bulbs?

b. What is the total resistance of the circuit?

c. What is the current in the circuit?d. What is the voltage drop across each

light bulb?e. What happens to the brightness of each bulb in a series circuit as additional bulbs are added? Why?

6V

3Ω

2A

2V

PARALLEL CIRCUIT• The different parts of the circuit are on separate

branches.• A break (like a burned out light bulb) in the

circuit does not stop the flow to the remaining devices.

• Multiple light bulbs will remain the same brightness since the resistance is not decreasing as it does in a series circuit.

• Each pathway can be separately switched off without affecting the others.

PARALLEL CIRCUIT• Household circuits – Wired in parallel, with a

standard of 120 volts.• Voltmeters are wired in parallel.

HOUSEHOLD CIRCUITS

• Many appliances draw electricity from the same circuit.

• If the wires get too hot due to too much electricity, a fuse can blow or circuit breaker can flip.

• Circuit Breaker – a piece of metal bends when it gets hot and “flips” the breaker to the off position.

• Fuse - a piece of metal melts when it gets hot and causes a break in the circuit.

PARALLEL CIRCUIT• The more paths the LESS

the resistance.–Water example again:

added pipes coming from a large tank will allow more water to flow out that a single pipe.

–Therefore as resistance decreases, current increases; they are inversely proportional.

PARALLEL CIRCUIT

RULES

1. Voltage is the same across each component of the parallel circuit.

2. The sum of the currents through each path is equal to the total current that flows from the source.

a. What is the voltage across each resistor?

b. What is the current in each branch?

c. What is the total current provided by the battery?

12V

6 A and 4 A

10 A

CIRCUITSSeries and Parallel Review

Question: What is the major difference between a series circuit and a parallel circuit – in your own words – put in your notes.

SCHEMATIC DIAGRAMS

• All circuit drawings need at least the following:–Power supply, wire, resistors, switches, other

items include connectors, meters, etc. • There is a set of standard symbols used to represent

these items in a diagram of the circuit.

SCHEMATIC DIAGRAMS

SCHEMATIC DIAGRAMS

• Draw a series circuit. Include a power source, wires, several resistors (light bulbs) and a switch.

SCHEMATIC DIAGRAMS

• Draw a parallel circuit. Include a power source, wires, several resistors (light bulbs) and a switch.

LIGHT BULB

Electricity flows through the circuit. If the bulb is broken, so is the circuit.

TRANSPORTING ELECTRICITY

A transformer is a device that increases of decreases alternating current generated by a power plant so it can enter homes safely.

VOCABULARY

Lightning Rod - a metal rod or metallic object mounted on top of an elevated structure, such as a building, a ship, or even a tree, electrically bonded using a wire to interface with the through an electrode, engineered to protect the structure in the event of lightning strike.

ELECTRICAL POWER

• The rate at which electrical energy is transferred by an electric circuit.

• Use Joule’s Law: Power = current x voltage.• Unit: watt, W• A kilowatt hour is what the power company uses to

determine how much electricity or energy you used.• Energy used = Power (kW) x Time (hours).• E= P x t• To find cost, you would multiply the energy by the

amount per kilowatt hour.

ELECTRICAL POWERPRACTICE

1. 105 V are used to power an appliance that needs 15.0 amps. What is the power used?

V = 105VP = ?I = 15.0amp

P = I x V

P = I x V = (15.0amp)(105V)

= 1575 W = 1.575 kW

ELECTRICAL POWERPRACTICE

2. How much energy is used when this appliance is used for 30.0 days, 24hrs a day?

E = ?Time = 30 days x 24 hours/day = 720hrP = 1.575kW

E = Power x time

E = P x t

= (1.575kW)(720hr)

= 1134 kW hour

ELECTRICAL POWERPRACTICE

3. If the power company charges 8¢/Kw-h, what is the cost of the energy above.

Cost = Energy x price per kW hr

E = 1134kW hourCost = ?Price = $0.08/kW hr

Cost = E x price

= (1134kW hr)($0.08/kW hr)

= $90.72

CIRCUIT PRACTICE

CIRCUIT PRACTICE

2. In this circuit, three resistors receive the same amount of current (4 amps) from a single source. Calculate the amount of voltage "dropped" by each resistor, as well as the amount of power dissipated by each resistor. The voltage drop is calculated by multiplying current in the circuit by the resistance of a particular resistor: V = IR.1Ω- ____________ 2Ω- ____________ 3Ω- ____________

CIRCUIT PRACTICE3. Use the series circuit pictured to answer questions a-e.

a. What is the total voltage across the bulbs? ___________

b. What is the total resistance of the circuit? ___________

c. What is the current in the circuit? _________

d. What is the voltage drop across each light bulb?

e. Draw the path of the current on the diagram.

CIRCUIT PRACTICE4. Use the parallel circuit pictured right to answer questions a-c.

a. What is the voltage across each resistor? ____

b. What is the current in each branch? ____

c. What is the total current provided by the battery? ______

CIRCUIT PRACTICE5. Use the parallel circuit to answer questions a-c.

a. What is the voltage across each resistor? ___________

b. What is the current in each branch?______________

c. What is the total current provided by the battery? _________