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)

23. Ohmmeter/multi meeter
An instrument for measuring resistance is called an ohmmeter.
multimeter basics

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

26. Series Circuit
An electrical circuit with only one path for the electrical current to follow
the objects are in series

27. 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 all the resistors that are present in the circuit.
Req = R1 + R2 + R3 … Rn

28. 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.

29. Questions?

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

31. Parallel Circuits

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

33. 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 equivalent resistance (total resistance) is equal to the sum of the inverses of the resistances in the branches

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

35. Parallel Circuits What’s the voltage drop across each branch? 9V
What is the current through each branch?
1) I = V/R = 9V / 10000Ω = .0009A = .9 mA
2) 4.5 mA
3) 9 mA
What is the total current though the circuit?
14.4 mA

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