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. Voltage
What is gravitational potential energy?

5. Voltage
Electrons moving through a conductor are driven by a certain pressure.
That pressure is often called a “tension” and is known as electrical potential difference
Units: volts (v)

6. Voltage
high tension power lines

8. Resistance
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.
Units: ohm (Ω)

9. Current
Current (I) is the amount of charge that actually moves through a conductor
Units: amperes, amps (A)

10. Current

11. Current

12. Current Everyday examples Hearing aid: 0.7 mA
Tungsten light bulb : 500–830 mA
Toaster: A
Hair dryer: 15 A

13. Ohm’s Law

14. Ohm’s Law
There is a relationship between tension (V), current (I) and resistance (R)
V = I R

16. Stun gun Output voltage: 100 V to 6 kV Current:100 to 500 mA
Duration:10 to 100 µs (microseconds);
electrical charge 15 to 500 µC
taser training 1
taser training 2

18. Electrical Power
Electric Power (P) is the rate at which electrical energy is used in a circuit.
Electric power = current x voltage
P = I V
The SI unit for power is watt (W)
If Ohm’s law is applied,
P = I2R

19. Electrical Power Power companies measure energy consumed.
They charge for energy used in the home, without regard for the work done with it (useful or not useful)
Energy = power x time
units (kwatt hours) (kWh)

20. 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, it can generate too much thermal energy and cause fires.
To prevent overloading circuits, two methods are used as safeties.

21. 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.

22. 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)