1. Current
Current Electricity - involves the flow of electrons in a conductor
Such movement of these free electrons creates an electric current

2. Simple Circuits
For electric current to flow, there has to be an unbroken pathway for it, a complete circuit.

3. Closed and Open Circuits
Closed Circuit - an unbroken path of conductors through which electric current flows
Open Circuit - a circuit with a break in the conductive path, so no current flows

4. Know Your Symbols Resistor Capacitor Switch Conductive Wire
Battery or Power Supply
Resistor
Capacitor
Switch
Conductive Wire

5. Electrical Power
When a charge moves in a circuit, it loses energy. Sometimes this is because the charge is being used to do useful work.
The electrical resistance of a conductor is the opposition to the passage of an electric current through it.
Electrical resistance shares some conceptual parallels with the notion of mechanical friction.
The SI unit of electrical resistance is the ohm (Ω),

6. Electrical Power
An instrument for measuring resistance is called an ohmmeter.
Resistance opposes the flow of electric current; therefore, electrical energy is required to push current through the resistance. This electrical energy is dissipated, heating the resistor in the process. 

8. Fuses and Circuit Breakers
Electric devices draw a certain amount of current in order to function.
If too many devices are put on a single circuit, the high current can overload the wires and cause fires.
To prevent overloading circuits, two methods are used as safeties.

9. Fuses and Circuit Breakers
A fuse is a device that contains a metal strip.
If the circuit gets too hot, the metal strip melts and opens the circuit.
A melted fuse is a sign that there is a short or an overload in the circuit.

10. Fuses and Circuit Breakers
A circuit breaker is a switch that opens a circuit automatically when the current exceeds a certain value
Unlike fuses, circuit breakers can be switched back on (to close the circuit)

11. Series Circuits
An electrical circuit with only one path for the electrical current to follow

12. Series Circuits Req = R1 + R2 + R3 … Rn
Equivalent resistance: the amount of resistance that a single resistor would need in order to equal the overall affect of the collection of resistors that are present in the circuit.
Req = R1 + R2 + R3 … Rn

13. Series Circuits
Current: the current in the circuit is calculated using Ohm’s Law and the equivalent resistance
The current remains the same throughout the circuit.
Voltage drops: Calculate the decrease in electrical potential energy across each device that has resistance by using Ohm’s Law.

14. Questions?

15. Parallel Circuits
An electrical circuit that provides more than one path for the electrical current to follow.

16. Parallel Circuits

17. Parallel Circuits
An electrical circuit that provides more than one path for the electrical current to follow.

18. Parallel Circuits Vtotal = V1 = V2 = V3 = Vn
The voltage drops of each branch equals the total voltage
Vtotal = V1 = V2 = V3 = Vn
The total current is equal to the sum of the currents in the branches
Itotal = I1 + I2 + I3 + In
The inverse of effective resistance (total resistance) is equal to the sum of the inverses of the resistances in the branches

19. Parallel Circuits
An electrical circuit that provides more than one path for the electrical current to follow.

20. Parallel Circuits What’s the voltage drop across each branch? 9V
What is the current through each branch?
1) .9 mA
2) 4.5 mA
3) 9 mA
What is the total current though the circuit?
14.4 mA

21. Parallel Circuits What is the equivalent resistance?
1/Req = 1/ / /1000
= 625 ohms