Unit D - Electricity Week 1

Static Electricity

I can… Distinguish between static and current electricity, and identify examples of each

Static electricity Static electricity is a stationary electric charge What does stationary mean? The charge is not flowing like a current Ex. Lightning, static electricity on clothing, “shocking people” by touching them, shock from your car.

Electrical charge Remember that opposites attract which is true of negative charges Most objects have an equal number of positive and negative charges so they are considered neutral When an object has more of one charge we say it is charged Ex. An object with extra electrons is negatively charged

Draw this picture in your Notes Draw this picture in your Notes! Positive Charge = Protons Negative Charge = Electrons

Electrical discharge Static electricity does not continue to flow, but it can undergo electrical discharge The build up charge on an object can be attracted to another object and jump to that object We call the spark an electrical discharge

Laws of electrical discharge Opposite charges attract each other Like charges repel each other

Charge separation Charged objects cause a charge separation when they are brought close to neutral objects For example, a negatively charged balloon, when brought close to a wall will cause the negative particles in the wall to be repelled, and therefore will be attracted to the positive particles left in the wall.

Review Questions What is the difference between a proton and an electron? What does it mean to be “statically charged”? How do like charges interact? How do unlike charges interact? A neutral object contains no charge. Is this true?

Salt and Pepper Activity Complete the Salt and Pepper Activity – This is due at the end of class.

Current electricity

I can… Distinguish between static and current electricity, and identify examples of each Identify electrical conductors and insulators, and compare the resistance of different materials to electric flow

Introduction https://www.youtube.com/watch?v=a3sviTa8hZw Is the charge on the eel a static charge or a current?

Electrical Current Static charges can discharge but they are not useful for operating electrical devices because they do not flow continually The steady flow or charged particles is called electrical current Electrical current can be used to run electrical devices as long as 2 things occur Need a source of energy Circuit must be closed

The necessary parts to a Circuit 1) Conductor- wire 2) Energy Source- battery or outlet 3) Load- the thing that uses the electricity 4) Control- often a switch

Conductor A conductor allows electricity to move through it easily What are examples of conductors? What is the opposite of a conductor? What are examples of these?

Insulators in an insulator the electrons are bound tightly to the nuclei so they resist movement

Conductors and insulators When would you want to use a conductor in a circuit? When would you want to use an insulator in a circuit?

Conductor and Insulator Sort Complete the Notebook Activity on Conductors and Insulators What about wearing a Suit of Armor in a Lightning Storm?

Superconductors Some metals are better conductors than others because they give less resistance to the electrons that are flowing Superconductors are perfect conductors- they have no resistance to electron flow Extremely low temperatures help reduce the resistance in the superconductors What’s the issue to running a superconductor at a low temperature?

Circuits A circuit is a path that controls the flow of electricity Usually electricity moves through solid wires but it can move through gases or other fluids Open and Closed Circuits

Open and Closed Circuits Complete the Smart Notebook Activity with Open and Closed Circuits

Quick Lab With a partner do the following lab– you have 20 minutes 1) Using any materials, make one light bulb light up 2) Using a battery, one bulb and 1 wire, make the light bulb light up 3) Using any materials, make 2 light bulbs light up 4) Make 2 light bulbs light up so that when you unhook one bulb, the other goes out 5) make 2 light bulbs light up so that when you unhook one bulb, the other stays on

Cells and batteries

I Can… Investigate and evaluate the use of different chemicals, chemical concentrations and designs for electrical storage cells. (explain functions of parts and diagram)

Electrochemical Cells An electrochemical cell is a package of 2 types of metals and an electrolyte One metal has more free for electrons than the other metal, so when a wire is attached to create a circuit the electrons get to move from one metal to the next, which creates a current There are 2 ends on a battery, Cathode = positive Anode = negative

Types of cells Cells can power tiny pacemakers, toys, cars or computers There are 2 types of cells 1) Dry cells- the electrolyte is a paste 2) Wet cells- uses a liquid electrolyte

Dry Cells The electrolyte in a dry cell allows ions to flow which completes the circuit An ion is an atom with a charge Positive terminal- where electrons travel back to the cell Negative terminal- where electrons travel from the cell

Dry Cells The 2 metals are called electrodes One electrode becomes positively charged, and the other becomes negatively charged. ALKALINE (having a basic electrolyte)- are some of the most common dry cells What does alkaline mean again?

Wet cells Wet cells often have a liquid such as sulfuric acid as their electrolyte They are usually cheaper and easier to make than dry cells but are more dangerous Vehicles use wet cells that need to be disposed of properly There are individual cells that alternate within the battery Each cell has a positive and a negative plate The terminals in the battery are at the top Think about it! Is it correct to call a car battery a battery?

Wet Cell Batteries

Answer to Think about It!

Primary vs. Rechargeable cells Primary cells: cells that can only be used one time Rechargeable cells aka secondary cells- can be reused, the chemical reaction that occurred originally is forced to go back so it can be used again Ni-Cd batteries are common secondary cells (made up of nickel and cadmium)

Battery Society today does not use the work battery correctly A battery contains more than one cell

Electrochemistry Alessandro Volta made the first practical battery around 1800 by stacking copper and zinc disks with an electrolyte solution Other scientists used batteries to split molecules into their elements electrolysis (ex. Water used as a fuel for rockets by breaking into oxygen and hydrogen) Electrochemistry was begun which is the study of chemical reactions involving electricity Scientists discovered that by putting more than one cell together they could increase the current and the power of the battery http://www.edumedia-sciences.com/en/media/670-electrolytic-conduction https://www.youtube.com/watch?v=8oeUE6dlP2A

Electroplating Electroplating uses the technology of a battery in reverse to create a layer of silver or gold on an object

How to electroplate The metal that is to be coated is immersed in an electrolyte solution with metal bar in it. The metal ions bond on the object and become a solid metal deposited on top of the less expensive materials http://www.youtube.com/watch?v=z7f7dQF2KLA

Controlling the flow of electrical current

I can… Draw and troubleshoot circuit diagrams for a variety of specific purposes. Explain how switches and resistors can control electrical flow, and predict the effects of these changes on output in a circuit.

A Unique circuit Neon signs have neon gas in them, when electricity is run through them they glow. The circuit needs to be complete and needs to be controlled carefully

Resistors Resistance is a measure of how difficult it is for electrons to flow through a substance A resistor uses power (a load can be a resistor) Resistance is measured in ohms –symbol Ω (omega) The more resistance a substance has the more energy it takes from the electrons that pass through it

Switches and Variable resistors Switches allow the control of a circuit by simply shutting it “on” or “off” A variable resistor or a rheostat can adjust the resistance in an object that the current flows through Ex. Volume control on stereos, dimmer light switch

Analyzing and building electrical circuits

I Can… Draw and troubleshoot circuit diagrams for a variety of specific purposes. Explain how switches and resistors can control electrical flow, and predict the effects of these changes on output in a circuit.

Types of circuits The most economical way to design a circuit is in a loop However, we do not always want every part of the circuit being dependent on the others in the circuit Ex. Would it be convenient for a plug-in to only work if the light switch was on?

Other types of Circuits Series Circuits Parallel Circuits http://www.edumedia-sciences.com/en/media/229-series-and-parallel-circuits

Series circuit In a series circuit there is only one pathway for the current If the pathway is interrupted the circuit cannot function Problem: adding more things increases the total resistance  light bulb will get dimmer as we add more

Parallel circuit Parallel circuits have a current path for each section of the current A break in one pathway does not affect the others Adding more pathways decreases the total resistance

Parallel vs Series Complete the Smart Notebook Activity using Series and Parallel Circuits http://cashmancuneo.net/flash/parallel.swf

Circuit drawing We use special (easy to draw) symbols to represent parts in a diagram An electrical diagram is called a schematic 4 parts of a circuit Source Conductor Switch or control Load

Lets draw parts for our Schematic Diagram

Tips for drawing schematics Conductors are always drawn in straight lines with 90 degree angles The symbols are made the same size Conductor lines are not allowed to cross

Example

Complete the Circuit Assignment in your notes. A closed circuit with a two-cell battery, a bulb and a switch. An open circuit with a three-cell battery, a bulb and a switch. A closed circuit with a three-cell battery, two bulbs, a switch and an voltmeter A circuit with a two-cell battery and two bulbs that can are controlled by one switch. A circuit with a three-cell battery and two bulbs, each of which are controlled independently by a switch.

Practice 1 Draw a schematic in a circuit made from: A battery 2 light bulbs A switch Conductors (Wires)

Practice 2 Draw a schematic diagram in a series including these things Resistor Switch Voltmeter Fuse Battery made of 3 cells

Practice 3 Draw a schematic diagram in parallel with the following: 2 cells that power the whole circuit A light turned on by one switch 2 more lights turned on by a switch together A third switch that turns on or off all the lights together

Lets read! As a class read about House Wiring and Microcircuits in your notes. What is a transistor? What is a microcircuit?

electrical safety

I can… Assess the potential danger of electrical devices, by referring to voltage and current rating (amperage) of the devices, and distinguish between safe and unsafe activities.

Review What is the difference between static and current electricity? What are some examples of conductors and insulators? What four things do we need to have in a circuit?

Electricity moves through the path of least resistance– where it is the easiest to flow A short circuit is a circuit where there isn’t any protection and the electricity moves quickly and can cause damage The 3rd prong on a cord leads to the ground and is called a ground wire http://www.edumedia-sciences.com/en/media/486-grounding-earthing

The number of amps of a current is more important in terms of the danger of being shocked Current from 0.015 A to 0.020 A will cause a painful shock and loss of muscles control What does this mean for a person being shocked? A current as low as 0.1 A can be fatal

The dangers of electrical shock To protect yourself from electric shock you never want to allow electricity to run through you Why are you safe in your car if a power line fell on it? When are you not safe?

Factors affecting electrical shock Different situations affect how bad an electrical shock is One a dry day with running shoes on you may just feel a tingle from an electrical fence, but the same fence on a rainy day when you are barefoot could really hurt

Protecting yourself from Electrical Shock Every plug in device in Canada must have a label on it showing what voltage it requires and what current it can use The higher these numbers the more harm it can do http://www.youtube.com/watch?v=n6DXkVY8fzs http://www.youtube.com/watch?v=DtoQbXzNqkg&list=PLyxsgbmjwCCkYdJ6Y2anojKwKXJVqiu9V

Plugs, Fuses and breakers Fuse: contain a very thin piece of metal that will melt if too much current flows through it stopping the circuit Need to be replaced (like in a car) Breakers- they “ short out” when too much current is sent through them Need to be cooled (like in your home)

Danger of lightning A lightning strike can give a current up to 30 000 A and it can kill Lightning usually strikes at the highest point on a horizon Lightning rods are connected to the ground through a wire to allow the discharge to dissipate to the ground http://www.youtube.com/watch?v=RLWIBrweSU8 http://www.youtube.com/watch?v=XKMdYbOfFzI

Demonstration Blow a Fuse! http://www.youtube.com/watch?v=ZT3HhDj8bRk http://www.youtube.com/watch?v=pJ9e4eaOiEk