1. Bellwork (3/5/14)  What are four voltage source examples? Please turn in the Dream Room Pre- Assignment.  D-cell battery.  Power lines.  Electric fence.  Car battery.

2. Electric Shock and Circuits 3/5/14

3. Dangers of Electric Shock Dangers of Electric Shock  Amount of current flowing through the body  Path of the current through the body  Length of time the body is in the circuit

4. Electric Current on the Body (aside: don’t need in your notes) Current (A)Effect Less than 0.001Unnoticed 0.001Can be felt 0.005Painful 0.01Muscle spasms 0.015Loss of muscle control 0.05Extreme pain, severe muscle reactions Greater than 0.1Can be fatal

5. AC and DC current  (AC) Alternating Current: Electric current that repeatedly reverses direction in a cycle (outlets)  (DC) Direct Current: Electric current that flows in one direction (batteries)

7. Rate of Charge Flow  In AC Circuits electrons just move back and forth in a cycle (50-60 times each second)  In DC Circuits electrons move about 3 cm/hr (~ 1 in./hr)

9. Why can birds sit on a wire?

10.  Electrical utility wires are NOT insulated!

11. Why can birds sit on a wire?  The bird becomes the same voltage as the wire.  The voltage difference between the feet is almost zero.  Feet are close together.  The bird has high electrical resistance.  But…

13. Bird on a Wire Diagram

14. Series Circuits  Current is the same throughout  Resistance increases as devices are added  Voltage is divided among all of the devices  Light bulbs would get dimmer as you add more  EX: Some holiday lights

15. Parallel Circuits  Current increases as you add in more devices and the total current equals the sum of all of the currents  Resistance decreases as you add in more devices  Voltage is the same for each device  Light bulbs would stay the same brightness as you add more  EX: Wiring of houses and buildings

16. Calculations (Dream Room)  Need to research the power in watts of each of your devices  Calculate the current (I) and the resistance (R) for each of the electric devices  Total current is the sum of all the currents  I total = I 1 + I 2 + … + I n  From total current find R eq (equivalent resistance)

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

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

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