1. Potential Difference, Current and Resistance
Voltage
Current
Resistance
How to Measure Voltage, Current and Resistance

2. Potential Energy Potential Energy = the energy stored in an object
Every electron has potential energy
Potential Energy = the energy stored in an object
Every electron has potential energy
Apple tree example
Apple tree
- two apples in a tree, one high and one low
both appes have energy stored in them
when the appe falls is converts its sotred energy into potential energy, into motion
Which Apple has the greatest potential energy and why?
Apple in a higher branch (more energy to convert, longer way to fall)

3. Potential Difference
Potential Difference or Voltage (V) = The source of energy in a circuit provides energy to the electrons. Voltage is described as the force that moves electric charges in a circuit. It is how much energy that the electrons pick up from the source.
igher the potential difference (voltage) the greater the potential energy of each electron
PD – another words = voltage
A battery had potential energy in the electrolyte of its electrochemical cells
The chemical in the electrolyte react with the electrode that causes a difference in the amount of electrons between the two terminals
One end has a negative charge (electrons) and the other end had the positive charge
The ngative electrons are attrached to the positive end of the battery and move toward it throught the use of a conductor (ie copper wire)
like falling apple from a tree
PD – causes current to flow in a closed circuit

4. Measuring Potential Difference
Volt (V) – is the unit used to measure potential difference
Voltmeter
Measures the potential difference between two locations in a circuit
A voltmeter is connected in parallel
What is the apparatus used to measure potential difference?
Placing the two end of the voltmeter and measure the potential differnece in a battery

5. Electrical Current
Electrical Current = is the number and speed of the electrons that are moving through the circuit.
Think of the continuous flow of electric current like water flowing in a stream
The water keeps flowing unless the source dries up
As long as the battery continues to separate charges on its terminals (ends) the electrons will continue to flow
WB – example of DC
WB – example of alternating current

6. Measuring Current
The electric current is measured in units called – Ampere (A) The symbol for current is I Ammeter- measures current in a circuit. An ammeter is connected is series.
Current
Energy moving past a point in the circuit every second

7. Resistance Conductors have low resistance values
Electrons are very small particles. They move very quickly through a circuit but can sometimes be slowed by larger objects that get in their way (like the nuclei of atoms). The ability to slow the movement of electrons in a circuit is called Resistance.
ALL SUBSTANCES RESIST ELECTRON FLOW
Conductors have low resistance values
Insulators have high resistance values
When a substance resists the flow of electrons, it slows down the current and converts the electrical energy into other forms of energy
The more resistance a substance has they more energy is gains from electrons that pass through it
The energy gains by the substance is radiated to its surroundings as heat and/or light energy
The more resistance a component has the smaller the conductivity

8. A Light Bulb Filament has a high resistance.
The loads in a circuit tend to have high
resistance, to slow the electrons
and convert the energy into a useable form of energy.
A Light Bulb Filament has a high
resistance.
- the current in a circuit passes thorugh the light bulb filament
The filament is a resistor, slows current flow
Converts the current into energy, heat up and produce light
WB other examples of resistance

9. Resistors
Resistors can be used to control current or potential difference in a circuit
The amount of resistance in a circuit affects the electrical current
Current decreases if you add resistance
Q: Another word fro potential differences
In a circuit electrons have a higher potential difference as tery enter a resistor compared to when they leave the resistor because they use up some energy passing through the resistor
Electrons enetering the resistorhave high potential energy
electrons exiting the resistor haave had their potential energy converted into another form of energy
Like the water flowing in a pipe
Thin pipe has more resistence = less flow
Thick pip has less resistance = more low

10. Factors Affecting Resistance
Table 11.1: Page. 443
Factor
How Factor Affects Resistance
Material
The material used in a circuit effects the resistance on the circuit
Copper is used most frequently as conducting wire
Temperature
High temperatures have a higher resistance
Low temperatures have a lower resistance
Length
Longer wires have more resistance
Shorter wires have less resistance
Cross-sectional Area
Wide wires have less resistance
Short wires have more resistance

11. Measuring Resistance Ohm (Ω) – the unit used to measure resistance
The symbol for resistance is R
Ohmmeter
Measures electrical resistance
Multimeter = measures differnece, current, or resistance
Ohm – greek leter omega

12. Homework Questions 3-5 pg. 438 Questions 1-3 pg. 442