CURRENT AND POTENTIAL DIFFERENCEText 11.1: 432-443

Agenda1. Inquiry – Pick an Electric Fish?!?!2. Current Electricity

Electric Circuits Electrochemical cells Potential Difference Electron Transfer – Measuring Current

3. Quick Lab – Using an Ammeter & Voltmeter

4. Check & Reflect Questions

Learning Goal

By the end of this class, we should be able to: Define and identify the correct units and

measurement tool of current Compare and contrast AC and DC current Identify the components of a simple current

and their functions

Inquiry – Pick an Electric Fish!?!

Elephantnose Fish Pacific Electric Ray Electric EelAnswer the following questions:- How do these aquatic species generate

electricity?- What do they use electricity for?

Current Electricity

The electricity produced by these animals is similar to static charge Unfortunately we cannot use

static charge to run electronic devices because it does not flow

It is STATIC!! To power electric devise you

need a steady flow of electrons

Electron Flow

Electrons will only continually move if 2 conditions are met:1. There is an energy

source2. There is a complete

track/path for them to flow through The path is called a

circuit The continuous flow of

electrons in a circuit is called current electricity

Electric Circuits A circuit always includes an

energy source, a conductor and a load An energy source provides

the energy to the circuit A conductor is the path

through which the energy flows

An electrical load is a device that converts electrical energy to another form of energy

Electric Circuits Many circuits also

include a switch A switch is a device

that turns a circuit on or off by closing or opening the circuit

Only when the switch is closed and the circuit is complete can electrons flow

Electric Circuits – Label It!

Electrochemical Cells – Converting

A simple electrochemical cell includes an electrolyte and two electrodes An electrolyte is a liquid or

paste that conducts electricity because it contains chemicals that form ions (EX: citric acid)

Electrodes are metal strips that react with the electrolyte. There are two electrodes in a battery, such as zinc and copper

Electrochemical Cells – Batteries

A battery has chemical potential energy in the electrolyte in its electrochemical cells Each electrochemical

cell is a package of chemicals that converts chemical energy into electrical energy that is stored in charged particles

Electrochemical Cells – Reaction The reaction

between the electrolyte and electrodes results in the electrons to collect on one electrodes (making it negative) and the other to be electron deficient (positive)

Types of Electrochemical Cells Wet Cell

Has a liquid electrolyte e.g. car battery

Dry Cell Uses a paste of a

liquid electrolyte

Fuel Cell Chemical reaction with

a fuel i.e. hydrogen

Electrochemical Cells – Label It!

Electrochemical Cells – Recycling 50% of all heavy

metals in landfills come from batteries

Contain toxic materials i.e. nickel, cadmium, and lead

What are some responsible options?

Electrochemical Cells – Inquiry Is it possible to charge an iPod from with

a piece of fruit?

http://www.youtube.com/watch?v=PuiPDBA3XZI

Learning Checkpoint Answer the following questions:

1. How is current electricity different from static electricity?

2. What is an electric circuit?3. List three components of an electric

circuit.4. What is the difference between an

electrolyte and an electrode5. Why should dry cells be recycled rather

than thrown in the trash?

Potential Difference Each electron has electric

potential energy Potential energy is energy

stored in an object i.e. battery

EX: An apple on a tree The higher the apple is the

more potential energy it has The potential energy can be

converted into another form of energy- like kinetic energy (motion)

Potential Difference – Voltage (V)

Battery = chemical potential energy in the electrolyte Difference of

electrons between (+) & (-)

Electrons are attracted to the positive terminal

Potential Difference – Voltage (V) Potential Difference or Voltage (V)

Electric potential between two points is called the potential difference or voltage.

Higher voltage = < potential energy of each electron

Must be measured across the load. Volts (V)

Electrons = Energy Transfer

So when you turn on a light switch, you close the circuit in wiring in the wall which turns on the light! BUT how does it

happen SO fast?

Electron Transfer – Hmmm… Think of it as a faucet /

hose If there is already water

in the hose - the water can come out of the end of the hose right away

The electrons do not travel from the switch to the bulb But from the wire right

near the bulb into it!

Electron Transfer – Electron Flow With electrons it is

similar When an energy source

is connected to a circuit, electrons in the conductor start to repel and push other electrons nearby

They push each other forward like you do in the café line!

Electron Transfer - Called Current!

Electric current is a measure of the amount of electric charge that passes by a point in an electrical circuit each second Like water in a stream Water keeps flowing

unless the source dries up i.e. electrons will continue to

flow until the battery stops separating charge

Electron Transfer – Current If electrons flow in one

direction it is called a direct current (DC) Like in batteries (low-powered)

If electrons can move back and forth at regular intervals called cycles are called alternating current (AC) i.e. big power lines

Electron Transfer – Current

Electron Transfer – Measuring Current

Current is measured with an ammeter Unit is amperes

(A) Black is negative

and red is positive when measuring an ammeter or voltmeter

Electron Transfer – Current vs. Voltage

An Ammeter measures the flow of electrons at any point in the circuit.

A Voltmeter measures the potential difference across the load

Where else could you measure Amperes?

Where else could you measure voltage?

Measuring Current Quick Lab

1. Build a circuit with one battery, one switch, and one bulb.

2. Open your circuit and connect the ammeter as show in diagram A.

3. Close and test your circuit. Record the current in amperes (A)

4. Repeat steps 2 and 3. This time connect the ammeter as shown in diagram B.

Measuring Voltage Quick Lab

1. Build a circuit with one battery, one switch, and one bulb.

2. Connect the voltmeter to the circuit as shown in diagram A

3. Close the circuit and record measurement

4. Repeat steps 2 and 3. This time connect the voltmeter as shown in diagram B.

Check & Reflect Answer the following questions in your

textbook: Q. 1, 2, 3, 4, 5, 6, & 12 page 447