An electric circuit is composed of 3 elements Conductor, potential difference, closed loop An electrical circuit without a load that has some resistance is essentially a short circuit (Think about the batteries in the simulation) (An ammeter has very little resistance. Think about my poor ammeters in a circuit with no loads or other resistance.) Electrical Circuits

In a series electric circuit all of the electrons must flow through the same elements In a parallel electric circuit electrons may flow through different circuit elements Electrical Circuits

In a series electric circuit, the voltage drops as it flows through each resistive circuit element Electrical Circuits

Resistors in Series: Building Analogy To go from the top to the bottom floor, all people must take the same path. So, by definition, the staircases are in series. With each flight people lose some of the potential energy given to them by the elevator, expending all of it by the time they reach the ground floor. So the sum of the V drops across the resistors the voltage of the battery. People lose more potential energy going down longer flights of stairs, so long stairways correspond to high resistance resistors. The double waterfall is like a pair of resistors in series because there is only one route for the water to take. The longer the fall, the greater the resistance. 3 steps 6 steps 11 steps Elevator (battery) R 1 = Lamp R 2 = Lamp R 3 = Lamp R1R1 R2R2

Diagramming circuits

Ohm’s Law: Ohm's Law …says that, for many materials under a wide range of conditions, the voltage, V, and current, I, are linearly related, which implies resistance, R, is independent of V and I. When does it not apply? (Most important case)

Ohm’s Law Mnemonic

Resistance and Ohm’s Law Resistance is the impedance to the flow of charge Resistance is defined as the ratio of potential difference to current R = V/I Unit is the Ohm, Ω A device is said to obey Ohm’s Law of its resistance is independent of the Voltage

Series Circuit Rules V T = V 1 + V 2 + V 3 + … I T = I 1 = I 2 + I 3 + … R T = R 1 + R 2 + R 3 + …

A + I 1 = 1 VV R 2 =V 1 = 9 V 2 = First, fill in all values of V and I. After review, fill in values of R

A A + I 3 = 2 VV VV V 4 = V 5 = 2 V 3 = I 2 = R 5 = R 4 = First, fill in all values of V and I. After review, fill in values of R. Assume all light bulbs have the same resistance.

A A + I 6 = VV VV V 7 = VV V 8 = 3 V 9 = V 6 = I 4 = 1 R 8 = R 9 = R 7 = A I 5 = First, fill in all values of V and I. After review, fill in values of R. Assume all light bulbs have the same resistance.

A A + I 6 = VV VV V 7 = VV V 8 = 6 V 9 = V 6 = I 4 = R 8 = 3 R 9 = 4 R 7 = 1 A I 5 = VV V 7 = R 7 = 2 We will work this one out together. Assume all light bulbs have the same resistance.

A A + I 6 = VV VV V 7 =3 VV V 9 = 5 V 10 =4 V 6 = I 4 = R 9 = R 10 = 4 R 7 = A I 5 = VV V 8 = R 8 = 2 Assume the light bulbs may have differing resistances. I T = I 1 = I 2 = I 3 = … V T = V 1 + V 2 + V 3 + … R T = R 1 + R 2 + R 3 + …

Questions What happens if we greatly increase the resistance? When else, besides electricity, do we see things like this? - Think about the effects on voltage (pressure), current (flow), and resistance (blockage)

Tell me about heart bypassess…

Parallel Circuit More than one path for the flow of charge More room for the flow of charge so Resistance goes down Voltage must stay the same since all sections have the same drop

R3R3 V2V2 A VV ITIT R1R1 A ITIT R2R2 VVVV V3V3 V1V1 Parallel Circuit: V oltmeters are parallel to the circuit I1I1 I 2 + I 3 ITIT How do the sum of I1, I2, and I3 relate to IT? Hint: What is current? What is it made up of? A AA

R3R3 V2V2 A VV ITIT R1R1 A ITIT R2R2 VVVV V3V3 V1V1 Parallel Circuit: V oltmeters are parallel to the circuit I1I1 I 2 + I 3 ITIT I T = I 1 + I 2 + I 3 by Conservation of charge (conservation of matter)

Parallel Circuit Rules V T = V 1 = V 2 = V 3 = … I T = I 1 + I 2 + I 3 + … 1/R T = 1/R 1 + 1/R 2 + 1/R 3 + …

R5R5 A ITIT R1R1 A ITIT R2R2 Parallel Circuit: Follow the current Now map the current flow for circuit 2 V 1, I 1 V 3, I 3 V 2, I 2 R3R3 R6R6 R4R4 A Circuit 2Circuit 1

R5R5 A ITIT R1R1 A ITIT R2R2 Parallel Circuit: Follow the current How does circuit 1 differ from circuit 2? V 1, I 1 V 3, I 3 V 2, I 2 R3R3 R6R6 R4R4 A

A ITIT R1R1 R 1 = 100 Ohms R2R2 V 2, I 2 V 1, I 1 VV VTVT R 2 = 200 Ohms I T = I 1 = I 2 = V T = 120V V 1 = V 2 = R T =

A ITIT R1R1 VTVT R2R2 V 3, I 3 V 2, I 2 R3R3 V 1, I 1 VV I T = I 1 = I 3 = V T = 120V V 1 = V 3 = R 1 = 100 Ohms R T = R 2 = 200 Ohms V 2 = I 2 = R 3 = 150 Ohms

A ITIT R1R1 VTVT R2R2 V 3, I 3 V 2, I 2 R3R3 V 1, I 1 VV I T = I 1 = 5A I 3 = 5A V T = 120V V 1 = V 3 = R wire = Ohms R T = R 2 = V 2 = I 2 = 5A R 3 = R 1 =

Resistance of an object What would we expect it to depend on? (Resistance is the impedance to the flow of charge)

Resistance of an object What would we expect it to depend on? (Resistance is the impedance to the flow of charge) A L

Find Resistance of a material Depends on four factors –R ∞ Temp –R ∞ RHO (ρ) resitivity –R ∞ Length –R ∞ A -1 (cross-sectional Area)

Low resistance Short Fat cold

High Resistance Long Thin Hot

Series and Parallel Circuits a L A L Parallel: Multiple Paths, low effective resistance Series: Single Path, high effective resistance

Resistivities at 20°C MaterialResistivity Aluminum2.82 × 10–8 Copper1.72 × 10–8 Gold2.44 × 10–8 Nichrome150. × 10–8 Silver1.59 × 10–8 Tungsten5.60 × 10–8 From Reference tables

Electrical Power P= IV “Poison Ivy”

Electrical Power Power is the rate at which work is done or energy is expended. –Unit is Watt = Joule / second –( James Watt worked on steam engines and launched the industrial revolution ) Electrical Energy = Power * Time = VIt

Electrical Power Electrical Power is priced in kWh –One kiloWatt = 1000 Watts –One kWh = One kW for one hour

Monthly Service Charge is $18 Central Hudson Variable Costs $0.047 $ $0.007 $0.004 $0.001 $0.003 $0.001 $0.004 $0.065 $0.014 Total$0.134

Monthly Charges – (Includes the effect of Schedules 59, 91, & 93) $6.00Basic Charge,plus $ per Kwh for the first600Kwhs $ per Kwh for the next700Kwhs $ per Kwh for all additional Kwhs Example - If you used1450 Kwhs of electricity, your bill would be calculated like this: Basic Charge=$6.00 $ x600Kwhs=$ $ x700Kwhs=$ $ x150Kwhs=$ Charge for1450Kwhs=$ (franchise fees not included)

Calculate your electrical cost List appliances you use Estimate wattage Estimate usage Calculate cost