1. Ch. 34
Electric Current

2. Electric Current Movement or “flow” of charge
Occurs when there is a difference in voltage between the ends of a conductor
Electrons carry charges through solid circuits

3. Electric Current (I) Current = charge I = q time t
Measured in amperes (amps or A)
Example: Calculate the current where 20 coulombs of charge pass a point in 8 seconds.

4. Electric Current (I) Current = charge I = q time t
Measured in amperes (amps or A)
Example: Calculate the current where 20 coulombs of charge pass a point in 8 seconds. 20 C / 8 s = 2.5 amps

5. Voltage Sources
Provide a potential difference so that charges are able to flow
Examples: Dry Cells or Wet Cells
Energy from a chemical reaction is converted to electrical energy

6. Voltage (V)
The potential energy per coulomb of charge available to electrons moving between terminals
Typical voltage in a home is 120 V
120 Joules of energy are supplied to each coulomb of charge that flows in a circuit!!!

7. Charge flows because of an applied voltage across the circuit
Remember that….
Charge flows because of an applied voltage across the circuit

8. Electric Resistance (R)
Measured in ohms, Ω
Depends on:
Conductivity of material
Diameter of wire
Thick wires have less resistance than thin wires
Length of wire
Longer wires have more resistance than shorter wires

9. Ohm’s Law I = V/R Current = Voltage / Resistance
Units: amps = volts / ohms

10. I = V/R
A 120 ohm heating element is powered by a 10 volt battery. What is the current?

11. I = V/R
A 120 ohm heating element is powered by a 10 volt battery. What is the current?
10 V / 120 ohm = amps

12. Alternating Current (AC)
Direct Current (DC)
Charge always flow in one direction
Ex. Batteries
Alternating Current (AC)
Charge alternates directions as it flows
Ex. Our outlets

13. Since our outlets produce AC current, but many appliances use DC, what can we do….. Convert AC to DC
Diode: a converter that only allows electrons to flow in one direction

14. Electric Power
The rate at which electrical energy is converted into another form
Power = current x voltage
P = IV

15. Ch. 34 Practice

16. Ch. 35 Electric Circuits
Series Circuits

17. For Problem Solving in Series
Resistances are ADDED
R1 + R2 + R3 = R total

18. The resistance of one lamp is 10 ohms
The resistance of one lamp is 10 ohms. What is the total resistance for the circuit shown?

19. The resistance of one lamp is 10 ohms
The resistance of one lamp is 10 ohms. What is the total resistance for the circuit shown? R total = = 30 ohms

20. The resistance of one lamp is 10 ohms
The resistance of one lamp is 10 ohms. What is the total resistance for the circuit shown? R total = = 30 ohms If the attached voltage source is 10 V, what is the current in the circuit?

21. The resistance of one lamp is 10 ohms
The resistance of one lamp is 10 ohms. What is the total resistance for the circuit shown? R total = = 30 ohms If the attached voltage source is 10 V, what is the current in the circuit? I = V/R I = 10 V / 30 ohms I = 0.33 amps

22. Parallel Circuits =
Rtotal R R R3

23. Parallel Circuits
The resistance of one lamp is 10 ohms. What is the total resistance for the circuit shown?

24. Parallel Circuits
The resistance of one lamp is 10 ohms. What is the total resistance for the circuit shown?
1/10 + 1/10 + 1/10 = 1 / Rtotal
0.3 = 1 / Rtotal
Rtotal = 1/0.3 = 3.33

25. Parallel Circuits
The resistance of one lamp is 10 ohms. What is the total resistance for the circuit shown?
Rtotal = 1/0.3 = 3.33
If the attached voltage source is 10 V, what is the current in the circuit?

26. Parallel Circuits
The resistance of one lamp is 10 ohms. What is the total resistance for the circuit shown?
Rtotal = 1/0.3 = 3.33
If the attached voltage source is 10 V, what is the current in the circuit?
I = V/R
I = 10 V / 3.33 ohms
I = 3 amps

27. Ch. 35 Lab and Practice