Unit D: Electricity Topic 1

Static Electricity All substances are made up of atoms, and some particles in the atom are positively and negatively charged. The positively charged particles are known as protons The negatively charged particles are known as electrons

Static Electricity Opposites attract. Electrons are attracted to protons Electrons are repelled from electrons Protons are attracted to electrons Protons are repelled from protons Equal amounts of protons and electrons makes an object neutral Charged particles exert force depending on their charge

Charged particles exert force depending on their charge Static Electricity Charged particles exert force depending on their charge A charged object brought close to an uncharged (neutral) object causes charge separation.

Static Electricity Balloon thought experiment: Imagine you rub a balloon against your hair. You are transferring electrons from your hair to the balloon. When you bring the charged side of the balloon near a wall, the negative charge of the balloon repels the electrons in the wall. This leaves the area of the wall closest to the balloon positive. The balloon and wall are attracted because of the opposite charges

Static Electricity Static electricity is a stationary electrical charge This means that static electricity does not flow! After a significant enough buildup of electrons, electrical discharge may occur in the form of a spark

Static Electricity The Laws of Electrical Charges 1) Opposite charges attract each other 2) Like charges repel each other

Static Electricity Demo!! Van De Graaf Generators: Use friction to build up static charges End of lesson 1

Questions (1-8) Check and Reflect p. 278

Current Electricity Electrical current is referred to as the steady flow of charged particles Electronic devices like your television or oven run on electrical current The two conditions that must be met for electrical current to flow are: 1) An energy source is required 2) A circuit (or path) for the charged particles to flow on needs to be complete Lesson 2

Quick Lab Follow the instructions on page 279 using the materials provided. See how many of the challenges you can complete in your groups. Science in Action 9

http://roguephysicist.com/building_circuits.htm

Current Electricity The rate at which an electrical current flows is measured in amperes (A) For example, there about 0.5A going through your average 60-Watt light bulb, and 5-8A going through your microwave when it is on Conductors are materials used to move electrical charge from point A to point B Examples of strong conductors: Silver, Copper, Mercury & Gold We use Galvanometers to measure amperes, or the current of electricity. Talk about how people steal copper- how its too expensive to make real copper pennies anymore Water hose - pressure of the hose represents voltage, flow represents amperage (current)

Current Electricity A circuit is the path that controls the flow of electricity Circuits are usually made of solid metal wires There are 3 common parts of circuits 1)conductor 2)energy source 3)load What are the parts of this simple circuit on the left? Retrieved from http://www.bbc.co.uk/staticarchive/1d60c4e10434d44ee0c3dcb5b7ccad4c1fee0771.gif

Current Electricity Voltage is the amount of electrical energy each charged particle carries, and is sometimes referred to as potential difference The higher the voltage, the higher the potential energy of each particle Voltage is measured in Volts (V) and is measured using voltmeters When using a voltmeter Red to positive Black to negative Red to positive Black to negative – for jump starting cars as well

Voltmeter Skill Practice End Lesson 2 Test various cells and measure their voltage readings using voltmeters. (p. 282) Remember, Red to Positive, and Black to Negative.

Check and Reflect p. 283

What is inside a 9V battery? Retrieved from https://www.reddit.com/r/pics/comments/37q5aa/cracked_9_volt_battery_reveals_6_aaaa_batteries/ 6 AAAA batteries! Why are batteries named ‘A’ ‘D’ etc. - because in 1940’s A was smallest size as things took lots of power, but then as we developed technology that required less voltage to operate, that is less charge per particle, we took up AA and AAA naming sequences to indicate smaller charge

Which is more dangerous, Volts or Amps?

Electrical Safety Amps are more fatal to humans than Volts Current as low as 0.1 Amps may be fatal High voltage is more dangerous than low voltage, however low voltage combined with high amperage can be more dangerous than just high voltage.

Electrical Safety A short circuit is when electricity takes an unintended path Electricity is dangerous when it decides to take a path to the ground through the human body Insulators help slow the flow of electricity Some examples of good insulators are: wood, rubber air Talk about how if you are wearing running shoes on a dry day and touch an electric fence – not as bad as touching it in your barefeet in the rain

Electrical Safety Fuses and circuit breakers are used to quickly interrupt a circuit when too much current (amps) are flowing through it Fuses contain a thin piece of metal that melts if there is too much current passing through Circuit breakers have wires that heat and trigger a spring that turns off a switch, cutting the electrical current

Steel Wool Fuse Demo

Exit Slip: Record 5 electrical safety pointers

Page 287 Questions 1, 2, 3, 4, 5, 7 & 10 Check and Reflect

Cells and Batteries An electrochemical cell is a package of chemicals designed to produce small amounts of electricity Used in pacemakers There are two main types of electrochemical cells: Dry Cells Wet Cells Both types of cells undergo chemical reactions which release free electrons

Cells and Batteries Dry Cells (primary cells) Dry cells contain chemical paste, and are sealed Made up of two different metals (electrodes) and an electrolyte Electrolytes are liquids or pastes that conduct electricity because it contains chemicals that form ions Remember that ions are atoms that become electrically charged by losing or gaining electrons

Cells and Batteries Dry Cells Continued The electrolyte of a dry cell reacts with the electrodes One electrode will become positively charged One electrode will become negatively charged The positive and negative electrodes are attached to the battery terminals Electrons leave through the negative electrode, and return through the positive electrode Give examples of types of positive and negative electrodes

Cells and Batteries Wet Cells (primary cells) Wet cells use liquid electrolytes, which are usually acidic The acidic electrolyte eats away at one electrode to donate electrons, and that electrode must eventually be replaced Electrons travel from the negative electrode and return through the positive electrode This is the same as dry cells Car batteries are examples of wet cells. In fact, car batteries use 6 lead-acid wet cells.

Cells and Batteries Rechargeable Cells(Secondary Cells) Rechargeable cells use external energy sources to reverse the chemical reaction, and restore the reactants necessary to produce electricity Not all chemical reactions are suited for rechargeable cells Rechargeable cells do eventually wear out over time

Cells and Batteries Batteries are connected cells 6V batteries are actually a compilation of four 1.5V dry cells Electrolysis is the splitting of molecules into their individual elements through electricity Chlorine is produced by electrolysis to make drinking water safe Rocket fuel is created through the electrolysis of Water Reflect back to environmental chemistry unit when talking about chlorine and drinking water.

Cells and Batteries Electroplating is the process of coating metal with a thin layer of silver or gold Sketch the process of electroplating

Cells and Batteries Anodizing is the process of coating aluminum with aluminum oxide. Electrorefining is used to remove impurities from metal. Galvanizing is the process of applying zinc onto metals like iron and steel.

Check and Reflect p. 294 1, 2, 3, 4, 6, 7, 10