1.1 – Static Electricity http://www.youtube.com/watch?v=fT_LmwnmVNM Static electricity is produced when two objects rub together This produces a buildup of charge on the objects being rubbed together http://www.youtube.com/watch?v=fT_LmwnmVNM

Electrical Charge Positive and negative charges on an object are due to the ratio of protons and electrons present in an object Objects are negative when they have more electrons than protons Objects are positive when they have more protons than electrons Objects are neutral when the amounts of positive and negative charges are equal

Producing a Charge Charges are produced when electrons move from one object to another An object that loses electrons becomes positively charged while one that gains electrons becomes negative Only the electrons move, never the protons! Not the protons!

Charge Separation

Electrical Discharge Static electricity generally does not move – it remains stationary (or is static) However, a built-up static charge on an object can be attracted to other objects and jump to the object Often this creates a small spark, which is known as an electrical discharge

Laws of Electrical Charges Opposite charges attract each other Like charges repel each other Neutral objects are attracted to charged objects

Water Demo What do we know about water molecules? Consider H20 as a compound. It is neutral…..or is it? Water is polar, although it is a neutural compound it has one slightly positive and one slightly negative end. Creating polarity.

Van de Graaff Generators A Van de Graaff Generator is used to study electrical charges A rubber belt running in the generator rubs against metal “brushes” and creates a static charge The charge is then transferred to the metal sphere, where the static charge builds up

Mythbusters Van de Graaff generator http://www.youtube.com/watch?v=7qgM1A3pgkQ

1.2 – Current Electricity Static charges do not work very well for operating electrical devices Electrical current is produced as charges move in a continuous flow An electrical current flows until it is used up or disconnected Think of it like water flowing until it is dammed or its source drives up

Amperes The rate at which current flows is measured in amperes (A) Called Amp for short Named after Andre-Marie Ampere Electrical current refers to the number of electrons passing a point in a circuit per second

How do we move electricity to its destination? CONDUCTORS Conductors are materials that electrical energy can move easily through

Circuits A circuit is a path that controls the flow of electricity (just like pipes and taps in a water system control the flow of water) In most pathways, electricity flow along solid metal wires, but circuits can also include gases, other fluids, special inks etc

Parts of a Circuit LOAD: a device that converts electrical energy to another form (ex. A lightbulb) ENERGY SOURCE: source of electrical energy (ex. Battery) CONDUCTOR: pathway for electricity to flow (ex. Wires)

Electrical Energy & Voltage Voltage is the measure of the amount of electrical energy carried by each particle Voltage is also known as “potential difference” The unit for voltage is known as the Volt (V) Voltmeters are used to measure voltage

Measuring Voltage When setting up a voltmeter, the red lead must run to the positive battery terminal, and the black lead should run to the negative terminal Some voltmeters have more than one red terminal. These are used to change the range of volatage readings on the voltmeter. For example, the meter could indicate either 0 to 5 V or 0 to 15 V depending on which red terminal is used. If you meter has several ranges you may not be sure which one to use. Start with the highest and work down until you get a clear reading.

1.3 Electrical Safety Electricity has the ability to seriously harm or kill This is because electrical current can interrupt the function of the nervous system and heart (both of which rely on their own electrical current to operate) https://www.youtube.com/watch?v=UE7R9AF0Wpw

Short Circuit A short circuit is an unintended pathway for electricity The current bypasses part of the normal circuit If a power line goes down, the electricity goes off in the entire area served by that power line. Without a complete circuit, electricity can’t flow. However, if the electricity can find another path, such as through a person’s body to the ground, then it will take that path.

Electrical Safety

Electrical Shock High voltage is more likely to cause damage than low voltage However, the number of amps is much more significant This is because you may only have a few high-energy electrons flowing through you if there is a high voltage and a low current However, high currents mean that lots of electrons are flowing through your body High voltage is more dangerous than low voltage – for example 50,000 volts is more likely to kill than 10 volts. However, even small voltages can kill if the shock carries a significant number of amps.

Electrical Shock The number of amps is much more important than voltage when assessing the potential danger of an electrical shock.

Protecting From Shock Insulators prevent the movement of electrical current and will protect you from electrical shock Current does not move freely through insulators such as wool, rubber, and air. https://www.youtube.com/watch?v=9iKD7vuq-rY The danger of electrical shock varies, depending on the situation. The current is greater when it can flow easily. Current does not flower easily through insulators. Other substances such as mud and damp soil conduct electricity somwhat.

Electrical Safety Pointers

Plugs, Fuses & Breakers The third prong on electrical plugs is the ground This provides a route through which excess charge can escape to the ground (instead of building up and discharging through you!) The grounded three-prong plug has an extra wire that connects the device to the ground wire of the building. (Leading to the ground) It provides another pathway for electricity just in case there is a short circuit in the device. It would be better to have electricity travel to the ground than through you!

Plugs, Fuses & Breakers Both fuses and circuit breakers limit the amount of current flowing through a circuit If a fuse or breaker receives too much current, the circuit is broken and the current stops

Plugs, Fuses & Breakers Fuses contain a thin piece of metal that is specially designed to melt if too much current passes through it. Household circuit breakers have a special wire that heats up if there is too much current. Instead of melting, the hot wire triggers a spring mechanism that turns off the switch inside the circuit breaker. As soon as the wire has cooled the breaker can be turned back on. Never turn a circuit breaker back on until you have fixed the problem that caused it to switch off.

Lightning The current in a lightning strike can be as high as 30 000 A To avoid being hit by lightning, avoid the following: standing on hilltops or under trees standing near metal objects People can survive lightening strikes when the full amount of current travels through only part or over the surface of their body. The best way to avoid a lightening strike is to avoid it! Lightening is a HUGE amount of negative charge and is seeking a high point to discharge

Lightning Rods Lightning rods are often added to tall building peaks They are connected to the ground with wires Any discharge from a lightning strike is conducted harmlessly to the ground (instead of destroying the building or its wiring)

Electrical Safety Electricity is no joke….unless you are Sheldon Cooper https://www.youtube.com/watch?v=a1jcjQGDwUI https://www.youtube.com/watch?v=WBBWCAx3qfk

1.4 – Cells and Batteries Some people have problems with the electrical signal that controls beating of the heart, a PACEMAKER can be surgically inserted to send small amounts of current to keep the heart beating normally The electricity use to operate a pacemaker comes from an electrochemical cell that supplies a steady current. An Electrochemical cell is a package of chemicals designed to produce small amounts of electricity. The tiny cells used in pacemakers are made with lithium and iodine and last from 5 to 12 years.

1.4 – Cells and Batteries An electrochemical cell is a device that provides a steady current that is produced by a chemical reaction Electrochemical cells come in two types: Wet cells and dry cells

Dry Cells A dry cell is an electrochemical cell that uses chemicals in a paste form The cell consists of two different metals and an electrolyte https://www.youtube.com/watch?v=9OVtk6G2TnQ An alkaline dry cell

Dry Cells An alkaline dry cell An electrolyte is a paste or liquid that conducts electricity because it contains chemicals that form ions.

Dry Cells - Terms An Electrolyte is a paste or liquid that conducts electricity because it contains chemicals that forms ions An Ion is an atom or group of atoms that has come electrically charge through the loss or gain of electrons An Electrode is a metal that the electrolyte reacts with As a result, one electrode becomes positvely charged and the other become negatively charged. These electrodes are connect to the cell’s terminals. Electrons leave from the negative terminal and return the postive terminal.

Wet Cells A wet cell uses an aqueous solution as the electrolyte Wet cells are less common than dry cells Why? They are not as reliable and can leak

Chemical Reactions & Electrochemical Cells In a wet or dry cell, the electrolyte reacts with the two metals One metal loses electrons and becomes positively charged The electrons are passed through the solution and are deposited on the other metal, which becomes negatively charged When connected to a circuit, the electrons leave the negative electrode and move through the circuit to the positive electrode

Battery Videos https://www.youtube.com/watch?v=9OVtk6G2TnQ

Rechargeable Cells Some dry and wet cells are primary cells (they cannot be recharged) Secondary cells (which are rechargeable) can regain stored charge if an electrical current is run “backwards” through the cell These cells use chemical reactions that can be relatively easily reversed Chemical reactions in a rechargeable cell can be reversed by using an external electrical source to run electricity back through the cell. The reverses flow of electrons restores the reactants that are used up when the cell produces electricity.

Batteries A battery is a collection of cells connected together “AA”, “AAA”, “C” and “D” type cells are not batteries – they are single electrochemical cells Larger batteries such as 9-V and 12-V batteries are true batteries

Batteries

Alessandro Volta Made the first practical battery He piled many copper and zinc discs on top of each other, separating them with electrolyte-soaked paper discs When scientists realized that connecting many cells together could produce more voltage and power, innovation soon followed. In 1807 this guy Humphry Davy, a professor in England, filled a whole room with 2000 cells to make one massive battery. Other scientists discovered electrolysis and electroplating.

Electrochemistry Is the study of chemical reactions involving electricity This was a whole new field of science including electrolysis and electroplating.

Electrolysis Electrolysis is a technique that is used to break free atoms from compounds This is done by running a current through the substance For instance, electrolysis can be used to produce oxygen and hydrogen from water Or separate pure metals from molten compounds Electrolysis- https://www.youtube.com/watch?v=7uIIq_Ofzgw

Electroplating Metals such as silver and gold are popular for use in jewelry and other decorative items but they are expensive. Less expensive versions can be made by coating cheaper metals with a thin layer of silver or gold. This is called electroplating. Often the cheaper metal is also stronger. A thin layer of metal can be plated onto a cheaper metal using electricity The item to be plated is immersed in an electrolyte along with an electrode that consists of the metal that will be used for plating Electricity flows from the plating metal to the object being plated, and as a result the metal moves across the solution and builds up on the surface of the object being plated Video- https://www.youtube.com/watch?v=OxhCU_jBiOA

Other Applications of Electrochemistry Anodizing – aluminum is coated with a layer of aluminum oxide, which is much harder than regular aluminum Electrorefining – impurities are removed from impure metals by placing the metal in an acid and running a current through it