ObjectiveObjective: : MCAS review- MCAS review-

ElectricityElectricity

HomeworkHomework::Go to bed earlyGo to bed early

Eat a healthy breakfastEat a healthy breakfast

Take out MCAS O.R. questionTake out MCAS O.R. question

Compare to other students’ workCompare to other students’ work

What would you rate each?What would you rate each?

What would you have scored?What would you have scored?

Scoring Guide - Score Point 4Scoring Guide - Score Point 3Scoring Guide - Score Point 2Scoring Guide - Score Point 1Scoring Guide - Score Point 0

5 Main Topics of Electricity on 5 Main Topics of Electricity on MCASMCAS

Circuits, Circuit diagrams, series vs. parallelCircuits, Circuit diagrams, series vs. parallel

Ohm’s Law and Electric PowerOhm’s Law and Electric Power

Static Electricity: Induction and ContactStatic Electricity: Induction and Contact

Coulomb's LawCoulomb's Law

ElectromagnetismElectromagnetism

circuit diagramscircuit diagramsIn circuit diagrams components are represented by the following symbols;

battery

Switch(open)

lamp

motorammeter voltmeter

resistor

Switch(closed)

Some diagrams use the resistor symbol as a symbol for a lamp or light (since a light bulb is in fact a resistor!)

wire

Electrical CircuitElectrical Circuit

A circuit is made up of a series of components A circuit is made up of a series of components all connected together and hooked up to a all connected together and hooked up to a power source (such a a battery)power source (such a a battery)

Any openings in a circuit and the circuit will Any openings in a circuit and the circuit will stop working! (open switch)stop working! (open switch)

Conductors like metal allow electricity to flow, Conductors like metal allow electricity to flow, but insulators (such as wood, plastic, rubber) but insulators (such as wood, plastic, rubber) stop flow of electricity.stop flow of electricity.

The components are connected end-to-end, one after the other.

They make a simple loop for the current to flow round.

SERIES CIRCUITS

If one bulb ‘blows’ it breaks the whole circuit and all the bulbs go out.

Voltage shared, current same

PARALLEL CIRCUITS

The current has a choice of routes.The components are connected side by side.

If one bulb ‘blows’ there is still be a complete circuit to the other bulb so it stays alight.Voltage same, current shared.

Ohms Law TableOhms Law Table

Resistance Current Voltage

Definition The opposition to the flow of charges

The flow of electrons through a circuit

Potential Difference ( the push behind electricity)

Symbol R I V

Equation

R = V

I

I = V

R

V = I R

MCAS formula sheet only gives MCAS formula sheet only gives one Ohm’s Law formula:one Ohm’s Law formula:

V = IRV = IR

So, set up triangle to solve for rest:So, set up triangle to solve for rest:

Also do same for Also do same for Power:Power:

P = VIP = VI

V

P

V I

++

+ --

-

--

---

-

Bringing Charges Together

++

+ ++

+Attract

RepelRepel

Charge by Induction:Charge by Induction:

-no contact-no contact

-no electron transfer-no electron transfer

-charged by “influence”-charged by “influence”

Charge by Contact:Charge by Contact:

-contact by items-contact by items

-electron transfer-electron transfer

-charged by gaining or -charged by gaining or losing electronslosing electrons

Contact

Charging by Charging by contact vs. contact vs. charging by charging by induction.induction.

Coulomb’s LawCoulomb’s LawMore charge = more force (multiplying together)

More distance = a lot less force (dividing by square of #)

When current flows through a wire When current flows through a wire you get a you get a electromagnetelectromagnet

3 things make magnet 3 things make magnet stronger:stronger:

- More currentMore current

- More loopsMore loops

- Metal core Metal core