Bellwork (3/5/14)Bellwork (3/5/14)

What are four voltage source What are four voltage source examples?examples?

Please turn in the Dream Room Pre-Please turn in the Dream Room Pre-Assignment.Assignment.

D-cell battery.D-cell battery. Power lines.Power lines. Electric fence.Electric fence. Car battery.Car battery.

Electric Shock and Electric Shock and CircuitsCircuits

3/5/143/5/14

Dangers of Electric ShockDangers of Electric Shock

Amount of current flowing through the Amount of current flowing through the body body

Path of the current through the bodyPath of the current through the body Length of time the body is in the circuitLength of time the body is in the circuit

Electric Current on the Body Electric Current on the Body (aside: don’t need in your notes)(aside: don’t need in your notes)

Current (A) Effect

Less than 0.001 Unnoticed

0.001 Can be felt

0.005 Painful

0.01 Muscle spasms

0.015 Loss of muscle control

0.05 Extreme pain, severe muscle reactions

Greater than 0.1 Can be fatal

AC and DC currentAC and DC current

(AC) Alternating Current(AC) Alternating Current: Electric : Electric current that repeatedly reverses current that repeatedly reverses direction in a cycle (outlets)direction in a cycle (outlets)

(DC) Direct Current(DC) Direct Current: Electric current : Electric current that flows in one direction (batteries)that flows in one direction (batteries)

Rate of Charge FlowRate of Charge Flow

In AC Circuits electrons just In AC Circuits electrons just move back and forth in a cycle move back and forth in a cycle (50-60 times each second) (50-60 times each second)

In DC Circuits electrons move In DC Circuits electrons move about 3 cm/hr (~ 1 in./hr)about 3 cm/hr (~ 1 in./hr)

Why can birds sit on a wire?Why can birds sit on a wire?

Electrical utility Electrical utility wires are NOT wires are NOT insulated!insulated!

Why can birds sit on a wire?Why can birds sit on a wire? The bird becomes the same voltage as The bird becomes the same voltage as

the wire. the wire. The voltage difference between the feet The voltage difference between the feet

is almost is almost zerozero.. Feet are close together.Feet are close together. The bird has high electrical resistance.The bird has high electrical resistance. But…But…

Bird on a Wire DiagramBird on a Wire Diagram

Series CircuitsSeries Circuits

Current is the same throughout Current is the same throughout Resistance increases as devices are Resistance increases as devices are

addedadded Voltage is divided among all of the Voltage is divided among all of the

devicesdevices Light bulbs would Light bulbs would get dimmerget dimmer as you as you

add moreadd more EX: Some holiday lightsEX: Some holiday lights

Parallel CircuitsParallel Circuits

Current increases as you add in more Current increases as you add in more devices and devices and the total current equals the the total current equals the sum of all of the currentssum of all of the currents

Resistance decreases as you add in Resistance decreases as you add in more devicesmore devices

Voltage is the same for each deviceVoltage is the same for each device Light bulbs would Light bulbs would stay the same stay the same

brightnessbrightness as you add more as you add more EX: Wiring of houses and buildingsEX: Wiring of houses and buildings

Calculations (Dream Room)Calculations (Dream Room)

Need to research the power in watts of Need to research the power in watts of each of your deviceseach of your devices

Calculate the current (I) and the Calculate the current (I) and the resistance (R) for each of the electric resistance (R) for each of the electric devices devices

Total current is the sum of all the currentsTotal current is the sum of all the currents IItotaltotal = I = I11 + I + I22 + … + I + … + Inn

From total current find RFrom total current find Req eq (equivalent (equivalent

resistance)resistance)

Schematic Symbols• Wires:• Connected wires:• Unconnected wires:• Resistor (elec. device):• Switch:• Battery / Outlet:• Circuit Breaker:• Multimeter:

Due DatesDue Dates

Circuits II H.W. – Circuits II H.W. – due Fri. 3/7/14due Fri. 3/7/14 Electricity Review – Electricity Review – due next Tues. 3/11due next Tues. 3/11 Electricity Test: M.C. & S.A. – Wed. 3/12Electricity Test: M.C. & S.A. – Wed. 3/12 Electricity Test: Problems – Thur. 3/13Electricity Test: Problems – Thur. 3/13 Dream Room Project – Dream Room Project – due next Fri. 3/14due next Fri. 3/14

CalendarCalendar

Today – Work on H.W. Circuits IIToday – Work on H.W. Circuits II Thurs. 3/6 – Work on H.W. or ProjectThurs. 3/6 – Work on H.W. or Project Fri. 3/7 – Electricity DemosFri. 3/7 – Electricity Demos Mon. 3/10 & Tues. 3/11 – ReviewMon. 3/10 & Tues. 3/11 – Review Wed. 3/12 – Electricity Test: M.C. & S.A.Wed. 3/12 – Electricity Test: M.C. & S.A. Thur. 3/13 – Electricity Test: ProblemsThur. 3/13 – Electricity Test: Problems Fri. 3/14 – Project Presentations Fri. 3/14 – Project Presentations