1. What is current?
&
Why does current flow?

2. Two positively charged particles Two negatively charged particles- - + + - + - + - + - + - + - + - + - + - +

3. Lots of Potential Energy
Proton (+)
Electron (-) + -
Metal Atom
Metal Atom + -
Lots of Potential Energy +
Metal Ion (+) - +
Metal Ion (-) + - + - + -

4. NOT exactly what happens The wire is made of metal – sea of electrons-
Metal Wire - + -
Neg +
Pos
NOT exactly what happens
The wire is made of metal – sea of electrons

5. Already FULL of freely moving electrons
1 amp = 1 C/s
6.24 x 1018 electrons
per second - - - - - - - - - - - - + - - -
The charge separation creates a push (voltage) that moves the electrons from negative to positive - -
Flow of Electrons (-) -
Flow of Current (+) - - - - - - - - - - - - - - -

6. The battery creates a charge separation
Series
Parallel
Battery
The battery acts as a “charge escalader” which recycles the incoming charged particle and does WORK on it – giving it some potential energy in the form of Voltage

7. Voltage (V) (Volts V) – Push which moves the charge
Current (I) (amps a) – Rate of flow of charge (e- / second)
~ Electrons must flow through a conducting material
~ Electrons flow from Neg  Pos
~ Current flows from Pos  Neg (by convention)
~ Higher current = brighter bulb
Resistance (R) (Ohms Ω) – Opposition to flow of charge
~ Greater resistance = lower current = dimmer bulbs
~ Objects (bulbs), type of wire, length of wire (nichrome)
~ Resistance decreases when wires are in parallel
Voltage (V) (Volts V) – Push which moves the charge
~ Related to the amount of work that can be done (PE)
~ Voltage drops across each resistor

8. Series Parallel SAME Current It = I1 + I2 + I3 Rt = R1 + R2 + R3
The current level is the same in all parts of the series circuit
Parallel
It = I1 + I2 + I3
Current from the series portion is split up between each parallel branch
Current
Rt R1 R2 R3 =
Resistance
Rt = R1 + R2 + R3
The resistance of each object is added together
(Rt) Will be treated as a single object in the series
More objects = Higher Rt
More branches = Lower Rt
Voltage
Vt = V1 + V2 + V3
SAME Voltage
All branches of the parallel “object” have the same amount of voltage
(Vt) is the voltage out of the battery. Each object (resistor) can have a different voltage

9. What is the relationship between
Current (I), Voltage (V) & Resistance (R) ?
In Series
More Bulbs = More Resistance (Opposition) = Lower Current
More Batteries = More Voltage (Push) = Higher Current
The amount of current (rate of flow) is a fight between voltage (push) and resistance (opposition)
V = I * R
I = V R
Ohm’s Law

10. How can we measure the resistance of an object?
1) In the lab activities = relative length of nichrome wire A1
Adjust the length of the nichrome wire until the two ammeters have the same current reading
UNITS = cm nichrome wire A2
Object
Nichrome
2) The multimeter has a setting (Ω) C A Ω
measured in parallel B D

11. SERIES: a circuit in which all parts are connected in a single loop
1 -Adding additional batteries in SERIES ___________ bulb brightness.
Increases
2 -Adding additional bulbs in SERIES ___________ bulb brightness.
Decreases
0.20 amps
0.17 amps
0.13 amps
Hypothetical currents
3 -As the current (amps) in a SERIES circuit increases, the bulb brightness _____________.
Increases
4 -The current (amps) anywhere in the SERIES loop is ____________.
The SAME

12. PARALLEL: a circuit in which different loads are on separate branches
PARALLEL: a circuit in which different loads are on separate branches. Any branch (split) can complete the circuit independently of the others.
1 -Adding additional batteries in PARALLEL ________________ the bulb brightness.
Does not change
2 -Adding additional bulbs in PARALLEL ________________ the bulb brightness.
Does not change
0.40
0.60
0.20
0.20
0.20
0.20
0.20
0.20
0.20
0.40
0.60
0.20
3 –If each of the bulbs have the same brightness, then the current must be ____________ for each separate branch (bulb).
The Same

13. Can there be too many bulbs?
0.40
0.20
0.20
0.20
0.20
0.20
0.20
0.20
0.40
???
No Bulb
Short Circuit
0.20
???
0.20
???
NOTE: We can not measure these currents
???
How much current now?
Do NOT test this, you can damage the ammeter!!!

14. SERIES (Loop) PARALLEL (Branches) Relative Brightness? 1.0 1.0 C A B
0.5
0.5 D
1.0
1.0 B
0.5
1.0
1.0 A C E
0.33 D F G
1.0
1.0

15. Examining Current & Resistance
Series
Parallel
Rt = R1+ R2
Rt R1 R2
= +
LCD
= 30 Ω + 10 Ω
= = =
= 40 Ω
Rt = = 7.6 Ω 4 30
Flip the Entire Equation Rt Rt
=  =

16. Calculating Vt & Rt In Series I = V R I = Rt = 9 Ω Rt = ? It = 1.33 A
It = All the SAME
I = V R
Vt = V1 + V2 + V3
3 V
Rt = R1 + R2 + R3
2 V
? V
9 V
12 V
5 Ω
1 Ω
3 Ω
I =
Rt = 9 Ω
Rt = ?
4 V
It =
1.33 A
12 V
2 V
6 V
? V
I =
4 V
12 V
7 Ω
I =
Rt = 21 Ω
Rt = ?
It =
0.57 A
I =

17. Calculating Vt & Rt In Parallel I = V R It = I1 + I2 + I3 4 A 8 = + +
2 Ω V 8
Vt = All the SAME
8 V
Rt R1 R2 R3 =
2 A
4 Ω V 8
2 V
I =
6 A
I = 10 A
8 V
2 Ω
4 Ω
7 A V 6
_____ Ω
0.857
8 V A 3 V 6
_____ Ω 2
I =
8 A
8 V
3 A
5 A

18. Rt = ( ) What is the total resistance (Rt) in the circuit? 3.08 Ω
PARALLEL (Branches)
SERIES (Loop)
Rt R1 R2 R3 =
Rt = R1 + R2 + R3
3.24 Ω
3.24 Ω
3.08 Ω
5 Ω
8 Ω Rt
= +
Rt = = 6.32 Ω +
Rt = ( ) -1
= 3.08 Ω
PARALLEL (Branches) are combined into a single OBJECT with a resistance that is always lower than the lowest resistance within the branches

19. What is the CURRENT and VOLTAGE across each resistor?
3.24 Ω V I R
= x
5 Ω
8 Ω
3.24 Ω
3.24 Ω
8 Ω
5 Ω
3.08 Ω
6.32 Ω
Rt = = 6.32 Ω

20. What is the CURRENT and VOLTAGE across each resistor?
3.24 Ω
I = = = 1.58 A
V V R
10.0 V V I R
= x
5 Ω
8 Ω
5.12 V
1.58 A
3.24 Ω
Series = Current is SAME
Parallel = It = I1 + I2 + I3
4.88 V
0.61 A
8 Ω
3.24 Ω is in series = 1.58 A
4.88 V
0.97 A
5 Ω
Series = Vt = V1 + V2 + V3
Parallel = Voltage is SAME
10V
1.58 A
6.32 Ω
Since the parallel OBJECT is in series with the 3.24 Ω resistor, the voltage of the 3.24 Ω + the voltage of the parallel object add up to 10 V
Series = Vt = 10 V = 5.12 V + parallel object
Since the 8 Ω and 5 Ω resistors are in parallel they have to be the same

21. + Rt = 10.315 Ω Rt = ( + ) = 1.875 Ω 1 1 2.5 7.5 Rt = ( ) = 1.45 Ω
What is the CURRENT and VOLTAGE across each resistor?
STEP 1: Find the total resistance
2.50 Ω
5.74 Ω
1.25 Ω
1.875 Ω
1.45 Ω
5.74 Ω
7.50 Ω
4.50 Ω
3.50 Ω
5.50 Ω
1.25 Ω
Rt = ( ) = Ω -1
Rt = Ω
Rt = ( ) = 1.45 Ω + -1
Rt R1 R2 R3 =
Rt = R1 + R2 + R3

22. What is the CURRENT and VOLTAGE across each resistor?
2.50 Ω V I R
= x
5.74 Ω
7.50 Ω
1.25 Ω
4.50 Ω
12.0 V
5.74 Ω
2.50 Ω
3.50 Ω
5.50 Ω
7.50 Ω
1.25 Ω
5.74 Ω
1.25 Ω
1.875 Ω
1.45 Ω
3.50 Ω
4.50 Ω
5.50 Ω
12.0 V Ω
Rt = Ω

23. What is the CURRENT and VOLTAGE across each resistor?
2.50 Ω V I R
= x
5.74 Ω
7.50 Ω
1.25 Ω
4.50 Ω
12.0 V
5.74 Ω
2.50 Ω
3.50 Ω
5.50 Ω
7.50 Ω
1.25 Ω
Series = Current is SAME
3.50 Ω
Parallel = It = I1 + I2 + I3
4.50 Ω
5.50 Ω
Series = Vt = V1 + V2 + V3
12.0 V Ω
Parallel = Voltage is SAME

24. 9 V
6 V
3 Ω

25. 9 V
6 V
3 Ω

26. push a certain number of electrons along
This flow of energy from the battery to power the light results in a decrease in the voltage (the energy level) of the battery. In other words, as a battery is used or discharged over time, the voltage drops as the anode and cathode undergo electrochemical changes.
This energy exchange will continue until the anode can no longer give up electrons and the cathode can no longer receive electrons. Once a battery reaches this state, the light bulb will no longer light up.
A battery is essentially a can full of chemicals that produce electrons. Chemical reactions that produce electrons are called electrochemical reactions.
Electrons collect on the negative terminal of the battery. If you connect a wire between the negative and positive terminals, the electrons will flow from the negative to the positive terminal as fast as they can (and wear out the battery very quickly -- this also tends to be dangerous, especially with large batteries, so it is not something you want to be doing). Normally, you connect some type of load to the battery using the wire. The load might be something like a light bulb, a motor or an electronic circuit like a radio.
Inside the battery itself, a chemical reaction produces the electrons. The speed of electron production by this chemical reaction (the battery's internal resistance) controls how many electrons can flow between the terminals. Electrons flow from the battery into a wire, and must travel from the negative to the positive terminal for the chemical reaction to take place. That is why a battery can sit on a shelf for a year and still have plenty of power -- unless electrons are flowing from the negative to the positive terminal, the chemical reaction does not take place. Once you connect a wire, the reaction starts. The ability to harness this sort of reaction started with the voltaic pile.
But most metals have electrons that can detach from their atoms and move around. These are called free electrons. Gold, silver, copper, aluminum, iron, etc., all have free electrons. The loose electrons make it easy for electricity to flow through these materials, so they are known as electrical conductors. They conduct electricity. The moving electrons transmit electrical energy from one point to another.
Electricity needs a conductor in order to move.
push a certain number of electrons along
apply a certain amount of "pressure" to the electrons
In an electrical circuit, the number of electrons that are moving is called the amperage or the current, and it is measured in amps. The "pressure" pushing the electrons along is called the voltage and is measured in volts. So you might hear someone say, "If you spin this generator at 1,000 rpm, it can produce 1 amp at 6 volts." One amp is the number of electrons moving (1 amp physically means that 6.24 x 1018 electrons move through a wire every second), and the voltage is the amount of pressure behind those electrons.
The battery provides the electromotive force (or e.m.f.) that "pushes" the electrons through the wires of the circuit. Electromotive force is measured in volts. In some ways it is similar to the potential energy stored in an object at the top of a hill. The object might roll down the hill and lose its potential energy and, in an analogous way, the electrons flow down the voltage drop (or potential difference) as they traverse the circuit.
As the charges move through the resistors (represented by the paddle wheels) they do work on the resistor and as a result, they lose electrical energy.
The charges do more work (give up more electrical energy) as they pass through the larger resistor.
By the time each charge makes it back to the battery, it has lost all the energy given to it by the battery.
Voltage:
The amount of work that each charge (mouse) will do as it goes through the circuit. Can also be thought of as the amount of push on the charges or how hungry the mice are.
Current:
The number of charges (mice) passing a point per second. The rate of flow of charges.
Resistance:
The opposition to the flow of charge. Any appliance that asks the charge (mouse) to do work will slow it down.

27. 9 V
6 V
3 Ω