Current and Potential Difference
description
Transcript of Current and Potential Difference
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