1. Chapter 34 and Chapter 35

2.  Circuit-Pathway for current

3.  Current-The rate at which a positive charge moves through a wire  Voltage-The energy needed to move a charge

4.  Direct current (DC)-Current traveling in 1 direction (from pos. to neg.)  Example: battery  Alternating current (AC)-Current that travels 1 way and then the other  Current changes from pos. to neg. and back to pos. 60 times a second

5.  The current flowing in a wire is directly proportional to the voltage across the circuit and inversely proportional to the resistance in the circuit  More potential difference (voltage)=more current  More resistance=less current

6.  V=IR  V=Voltage (V)-potential difference (build up of electrons)  What supplies the “push” that makes current move (like the water behind a dam or pressure supplied by a pump)  Shown as…

7.  V=IR  I=current (A)-the rate of flow of charge for the conventional (positive) current  Like water in pipes or a hose

8.  V=IR  R=resistance ( Ω called Ohms)-Opposes the flow of current  Like a kink in a hose  Shown as….

9.  What is the resistance of an electric frying pan that draws 12 amperes of current when connected to a 120 volt circuit?

10.  If the resistance of your body were 100,000 ohms, what would be the current in your body when you touched the ends of a 12 volt battery?

11.  Resistivity of the material  Area the current flows through  Length the current must travel

12.  R= ρ l/A  R=resistance ( Ω)  ρ=resistivity (Ωm)-depends on material  l=length (m)  A=cross sectional area (m²)  Area of circle: A=лr²

13.  The resistivity of copper is 1.76 X 10^-8 Ωm. What is the resistance of a coil of copper wire of total length 5.5 m and diameter of.0041 m?

14.  What is the resistance of a coil of copper wire that is 5 m long and has a resistivity of 2.5 X 10^-5 Ωm if the radius of the wire is 0.02m?

15.  What happens to the resistance when:  The length of the wire increases?  Resistance increase  Resistivity increases?  Resistance increases  Area increases?  Resistance decreases

16.  Open circuit-An “opening” or break in the wire causing NO current to flow  Example: Turning a switch off  Closed circuit-A continuous wire allowing current to flow  Example: Turning a switch on

17.  Series circuit-2 or more resistors in the same wire (without a split in the wire)  Only 1 path for the current to go  Christmas lights example

18.  The resistance in a circuit is the sum of the individual resistances (R Total=R1+R2+R3+..)  The battery voltage is the sum of the voltages (Voltage Total=V1+V2+V3+…..)  The current is the same everywhere in the circuit (I total=I1=I2=…)  Use Ohm’s Law

19.  Parallel circuit-2 or more resistors in a circuit on different wires (split wire)  2 or more paths for the current to go with ONLY 1 resistor in each path  Christmas lights: What happens when 1 light goes out?

20.  The total current is the sum of the individual currents (I Total=I1+I2+I3+…)  The voltage is the same throughout the circuit (V Total=V1=V2=V3=…)  The total resistance in a circuit is the sum of the individual resistances (1/RT = 1/R1 + 1/R2 + 1/R3 +…)

21.  Combination circuit-Series circuit + parallel circuit

22.  Ammeter-an electrical instrument used to measure current  Low internal resistance  Connected in “series” (in-line) with other circuit elements  Voltmeter-measures the voltage in a parallel circuit  High internal resistance  Connected “in parallel” (across) other circuit elements

23.  Power (W or “watts”)-The rate which energy is produced or consumed  Turned from one form into another  Example: Current to heat  Power=IV  P=I ²R

24.  What is the total power of the resistors in a wire that has a current of 3.5 A and a total resistance of 34.3 Ω?