CIRCUITS: Series & Parallel - SMCISD

CIRCUITS: Series& Parallel

Last Week’s BIG IDEAS: Oppositecharged objectsattract Like chargedrepelobjects

Last Week’s BIG IDEAS:electrons are the The“loose” particles thatmove to make thingscharged not theprotons. Protons arelocked in more solidrelationships in thenucleus and don’t “getaround”.

Last Week’s BIG IDEAS: The attractive forcebetween particles/objectsdepends on the amount ofcharge (in Coulombs) theobjects have and thedistance (in m) betweenthe two particles/objects. The above relationship isCoulomb’s Lawcalledand is given by:𝒒𝟏 𝒒𝟐Fe k 𝟐𝒓

Last Week’s BIG IDEAS:Coulomb’s Law ofattraction:Fe k 𝒒𝟏 𝒒𝟏𝒓𝟐For the eensy-beensyparticles like atoms,electrons, andprotonsNewton’s Law of UniversalGravitationIs a lotlike Fg G 𝒎𝟏 𝒎𝟐𝒓𝟐for the “big” particles likeplanets.The only difference is that Newton’s Law is only attractiveattractive andand Coulomb’s Law can be bothrepulsive.

Last Week’s BIG IDEAS:particles to some degree Planets behave like

Last Week’s BIG IDEAS:Both Coulomb’s Law of𝒒𝟏 𝒒𝟏attraction - Fe k 𝟐𝒓and Newton’s Law of Universal𝑚 𝑚Gravitation - Fg G 1 2 2𝑟are examples of forces at adistance(faraway) where the objects arenot touching and can be faraway.These are different fromcontactforces suchas friction, tension, force ofpush or pull in which theobjects are in direct contactwith each other.

Voltage (Electric Potential Difference),Current, and ResistanceWhat is this illustration showing? What does voltage do?What does current (ampere) represent? And what doesresistance do?

VOLTAGE (ELECTRIC POTENTIAL DIFFERENCE)elastic potentialElectric potential energy is likegravitational potential energyenergy andGPEHigherPotentialEnergy LowerPotentialEnergy-ELPEEPE

VOLTAGE (ELECTRIC POTENTIAL DIFFERENCE)To cause movement of a charge, there must be anelectric potentialdifference between twopoints in the electric circuit just as there could be awater pressure betweendifference intwo points in a plumbing system.

VOLTAGE (ELECTRIC POTENTIAL DIFFERENCE)In the image below, there is more electrical “pressure” at the6 V side of the battery than the 0 V side. Imagine that the 6negativelyV side is(-) charged and so electrons arepushed away (like charges repel) through the circuit towards thepositivelyside of the battery which is( ) chargedattractedto which the electrons are (oppositechargesattract).

VOLTAGE (ELECTRIC POTENTIAL DIFFERENCE)two paths theyIn this circuit the energetic electrons havecan go through. In the middle of each path is something that isresistingthe flow of electrons and thus they struggle touse upget through. In the struggle they someof theirelectrical energy which turns into light andenergy.heatworkThe electrons are moving slower after the(inJoules) they have performed.DIRECTIONS:Use the rightterms below in theblanks aboveWORD BANKresistingtwoUse upworkheat

VOLTAGE (ELECTRIC POTENTIAL DIFFERENCE)Navy nuclear submarine crew thatSuppose there was a U. S.just happened to be all guy sailors. They just got off their 3-monthrepelledtour on their boat and arefrom the sight ofeach other. They are seeking out members of the oppositesexandgo down to the only two clubs on this small islandusedthey are docked at to party-hardy. Once they’veupsubmarinetheir energy they head back tired to their .DIRECTIONS:Use the rightterms below in theblanks aboveWORD BANKsexsubmarineNavyrepelledused

VOLTAGE (ELECTRIC POTENTIAL DIFFERENCE)Potential energyPotentialenergy For example, to push apositively chargedStyrofoam pellet into apositively chargedelectric field requireswork(a forcethrough a distance) The Styrofoam gainselectrical potentialenergy in the process Since like chargesrepel the charged,Styrofoam moves awayfrom the Van de Graafgenerator convertingits electrical potentialkineticenergy intoenergy

VOLTAGE (ELECTRIC POTENTIAL DIFFERENCE)DIRECTIONS: Put the correct term in the correct blank below.WORD BANKrandomsectionPromspeedsopenopenIn an electrical circuit, while the switch is : Free electrons (conducting electrons) are always moving inrandommotion.speeds The randomare at an order of 1,000,000 m/s. There is no net movement of charge across a crosssectionof a wire. It is all back and forth and random. Its like the random movement of single kids dancing at .Prom

VOLTAGE (ELECTRIC POTENTIAL DIFFERENCE)closed What occurs in a wire when the circuit switch is ?An electric field is established instantaneously (at almost the speed oflight 3x108 m/s).,Free electrons, while still randomly moving, immediately begindrifting due to the electric field, resulting in a net flow of charge.They are likeusers who think have free will but are in factbeing manipulated to move in certain directions.Average drift velocity is about 0.01cm/s. The effect of the manipulationon FB users is small but since there arebillions of them, likeelectrons, the overall effect is large.WORD BANKusersclosedlightfreebillions

VOLTAGE (ELECTRIC POTENTIAL DIFFERENCE)What occurs in a wire when the circuit switch isclosed and electricity begins to flow?Much like a group ofstudents going to thebus circle afterschool, they slowly drift outat school in a messy butdeliberate pattern. Theelectric field is kind of likemonitorshalltelling students to go homeand get out of the E/electric/imgele/micohm.gif

VOLTAGE (ELECTRIC POTENTIAL DIFFERENCE)The electric potential V (or voltage) is thepotential for creating electric potential energy if acharge is placed at a given point. It is defined asthe energy per unit charge:𝑼𝒆𝒍𝒆𝒄V 𝒒Where Uelec is the electricpotential energy (in Joules) andq is the charge of an object inCoulombs.1 volt 1 V 1 Joule per Coulomb, 1 J/CAn electric field exerts an electrical force FE on a charge q.An electric potential V tells how much electrical energy Ueleceach charge q has.

VOLTAGE (ELECTRIC POTENTIAL DIFFERENCE)Another definition .pressureVoltage: Electrical “ ”thatpushes charges along a conductingpathway.Metric Unit for Voltage: Volt (V)

Electric Charges always travel from a electricalhighpressure region to alow pressure region.

CURRENTElectric Current: The flow of electrons through a conductingelectrons pass a givenpathway. It relates to how manyplace in a wire in one second.Metric Unit for Current: 1 ampere (A) 6.24 x 1018 e-/s1 AMPERE of current carries aboutelectrons per second

RESISTANCEresistResistance: The tendency of a substance tothe flow of e-s.Metric Unit: The force opposing e- movement is measured inOhms (Ω) .

RESISTANCEAll materials have some resistance, insulators have alarge amount of resistance, while conductors have verylittle resistance . As e-s flow through material and collidewith atoms, electrical energy is converted into two formsof energy:and.heatlight

RESISTANCEThe electricity has two paths to flow through. The 10 Ohmthree timesresistor allowsas many electrons/ions toflow as the 30 Ohm resistor.

RESISTANCEVariable resistor – The knob turning is applying variableresistance to the circuit. This can be seen because thelightlevel of the LED is fluctuating. Thevariable resistor is controlling the number of(e-s) passing through the circuit, or, inelectronscurrentother words, the(in Amps).

CURRENT, VOLTAGE, & RESISTANCEMake an analogy for voltage, resistance, and current like theones below

ElectricalCircuits

Circuit ONS: Draw lines from each term tothe corresponding item in the circuit diagramat right

Three general types of circuits:DIRECTIONS: Put the correct term in the correctblank below.WORD BANKPower sourceShortresistanceClosedcurrentOpenClosed Circuit - There is a complete loop with wires goingfrom one side of the power source through a resistor(s) to theother side of the .Open Circuit - There is not a complete loop for toflow.Short Circuit - There is a complete loop, but it does notcontain any to the flow of electricity.

Three general types of circuits:WORD BANKPower sourceShortresistanceClosedcurrentOpenClosed Circuit - There is a complete loop with wiresgoing from one side of the power source through aresistor(s) to the other side of the .Open Circuit - There is not a complete loop forto flow.Short Circuit - There is a complete loop, but it does notcontain any to the flow of electricity.Only WorkingCircuit

There are two ways to putresistors into a circuit.1. Resistors can bein seriesOR2. Resistors can bein parallel

Resistors in SeriesResistors are considered to be in series if thecurrent must go through all of the resistors inorder.The current (amps) through all resistors in seriesis the same.The voltage across resistors in series may bedifferentThe rate of electron flow (or current) isdetermined by which resistor?R3R2R1Ans. The resistor with the largest amount ofohms.

Combining (adding) ResistorsSeries ResistorsR1R2To find the total current just add upthe currents through each resistor:Itotal I1 I2 I3To find the total resistance, just addup the resistances of each resistor:Req Rtotal R1 R2 R3R3AmpsVoltage is calculated with Ohm’s LawI 𝑽𝑹Q

Resistors in ParallelResistors are considered to be in parallel if thecurrent is shared between multiple resistors.The current (amps) through all resistors in parallelmay be different.The voltage across all parallel resistors is the same.Will a resistor with a large resistance have more orless current through it then a resistor with a smallresistance?Ans. The resistor with a largeresistance will have a smallercurrent then the resistor withthe smaller resistance.R1R2R3

Combining (adding) ResistorsParallel ResistorsCurrent is calculated with𝑽Ohm’s Law: I 𝑹R1R2R3Total resistance:1111 Rtotal R1 R2 R3Vtotal V1 V2 V3

Example 1: A circuit has threeresistors - an 8.0 W, 5.0 W and a 12W resistor - in series along with a24 V battery.Draw the circuit.Calculate the total resistance of the circuit.Calculate the total current through the circuit.What is the current through each resistor?Calculate the voltage across each resistor.

P.O.D. 1: A circuit has threeresistors - a 6.0 W, a 4.0 W and a 9 Wresistor - in series along with a 36V battery.Draw the circuit.Calculate the total resistance of the circuit.Calculate the total current through the circuit.What is the current through each resistor?Calculate the voltage across each resistor.

Example 2: A circuit has threeresistors: 6.0 W, 4.0 W and a 12 Wresistors in parallel along with a 24V battery.Draw the circuit.Calculate the total resistance of the circuit.Calculate the total current through the circuit.What is the voltage across each resistor?Calculate the current across each resistor.

P.O.D. 2: A circuit has threeresistors: 4.0 W, 6.0 W and a 8 Wresistors in parallel along with a 30V battery.Draw the circuit.Calculate the total resistance of the circuit.Calculate the total current through the circuit.What is the voltage across each resistor?Calculate the current across each resistor.

Electrical OutletsElectrical outlets provide electric potential (orthe voltage) for any appliance plugged in to it.In the United States ALL outlets provide 120 V(in Europe it is 240 V)

Example 3: What will the current be if anAmerican-made 55 W light bulb is plugged into a 220 V power source? We have worked with Power before in our Energy Unit.It is measured in Watts𝑾It was given by the formula P 𝒕For electricity we have three alternative “shortcut”formulas for Power based on what is given in the problem:P I2 R , P I V , P 𝑽𝟐𝑹For this problem we use which one?P I V𝑷Solving for I I SOLUTION: I 𝑷𝑽 𝟓𝟓 𝑾𝟐𝟐𝟎 𝑽𝑽 0.25 Amps

P.O.D. 3: What will the resistance be if aEuropean-made 55 W light bulb is plugged into a 210 V power source? What about anAmerican-made 55 W light bulb?

MULTIPLE CHOICE: As more identical resistors R are addedto the parallel circuit shown, the total resistance betweenpoints P and Q R1. Increases2. Remains the sameQ 3. DecreasesP