Science 9 Unit D Electrical Principles and Technology What is electricity? Electricity is the flow of electrons. Lightning Lightning is one of the most beautiful displays in nature. It is also one of the most deadly natural phenomena known to man. With bolt temperatures hotter than the surface of the sun and shockwaves beaming out in all directions, lightning is a lesson in physical science and humility. Electrical Storms In an electrical storm, the storm clouds are charged like giant capacitors in the sky. The upper portion of the cloud is positive and the lower portion is negative. How the cloud acquires this charge is still not agreed upon within the scientific community. All that is needed now is a conductive path for the negative cloud bottom to contact the positive earth surface. The strong electric field, being somewhat self-sufficient, creates this path.

LIGHTNING MYTH #1 The tallest objects in a storm don't always get struck by lightning. It's true that taller objects are closer to the clouds, but as discussed previously, lightning can strike the ground at a close distance to a tall object. Taller objects may have a higher possibility of a strike, but where lightning is concerned, the strike path is not predictable. Any time there is an electrical current, there is also heat associated with the current. Since there is an enormous amount of current in a lightning strike, there is also an enormous amount of heat. In fact, a bolt of lightning is hotter than the surface of the sun. This heat is the actual cause of the brilliant white-blue flash that we see.

Thunder is the shockwave radiating away from the strike path. When the air heats up, it expands rapidly, creating a compression wave that propagates through the surrounding air. This compression wave manifests itself in the form of a sound wave. The Danger of Lightning A lightning strike can have 20,000 A to 200,000 A- more than enough to kill you. Avoid being the target of a lightning strike, by staying low to the ground (horizon) and away from trees. Lightning can also do a lot of damage to a building. Metal lightning rods, that are connected to the ground with a grounding wire are fixed on the roof of many buildings to prevent damage to the building during an electrical storm. Static Electricity When you get a 'shock', feel a 'jolt' or a 'spark', you are experiencing the same type of electrical effect that makes lightning. Static electricity happens when there is an imbalance of electrons (which have negative charges). Static electricity is the imbalance of positive and negative charges Thales’ Amber The first person known to have experimented with static electricity was the philosopher Thales around 600 B.C. He found that rubbing amber, a fossilized tree resin, caused it to attract some materials. The word electricity is from the Greek word for amber, elektron. Electrical Charge Most objects have the same number of positive (proton) and negative (electron) charges. This makes them neutral (no charge). When there is a difference in the electrical charge, certain actions are predictable, because of The Laws of Electrical Charges. Positively Charged Neutral Charge Negatively Charged

The Laws of Electrical Charges • Opposite charges attract each other. • Like charges repel each other.

Static electricity is usually caused when certain materials are rubbed against each other, like wool on plastic or the soles of your shoes on the carpet. The process causes electrons to be pulled from the surface of one material and relocated on the surface of the other material. The material that loses electrons ends up with more positive (+) charges. The material that gains electrons ends up with more of negative (-) charges on its surface. Why a charged balloon clings to a wall Charge separation occurs, when a charged object is brought close to a neutral object. The charged electrons repel the electrons in the neutral object and the charged object is then attracted to the protons of the neutral object (balloon on a wall) Static Electricity Prefers dry air When the air is humid, water molecules can collect on the surface of various materials. This can prevent the buildup of electrical charges. This has to do with the shape of the water molecule and its own electrical forces. Thus, static electricity is formed much better when the air is dry or the humidity is low. Prefers dry air When the air is humid, water molecules can collect on the surface of various materials. This can prevent the buildup of electrical charges. This has to do with the shape of the water molecule and its own electrical forces. Thus, static electricity is formed much better when the air is dry or the humidity is low. Electrical Discharge is the movement of charges whenever an imbalance of charges occurs. The action results in neutralizing the objects. The over-charged electrons repel the electrons in the object and the positive protons attract the charged electrons causing a discharge or 'miniature lightning bolt'.

Generating Static Electricity Van de Graaff (VDG) Generators These generators build up an excess of static charge using friction. A rubber belt rubs a piece of metal and transfers the charge to a sphere. When you touch the sphere the charge builds up on you. Remember! - like charges repel - that is why your hair strands separate as you touch the sphere as the charge builds up on your body. Tesla Coils A Tesla coil is an electrical resonant transformer circuit invented by Nikola Tesla around 1891. It is used to produce high-voltage, low-current, high frequency alternating-current electricity Cleaning the Air In the early 1900s, factories with large smoke stacks were belching pollutants into the atmosphere. In 1907, Frederick G. Cottrell patented a device called the electrostatic precipitator. It not only cleaned the air, but also recovered products from the smoke that would otherwise pollute. Electric Eels Certain animals, namely, the electric eel, can produce electric shock, to kill or stun prey. They have a special organ that contains specialized muscle cells called electroplaques. Each cell produces a small amount of electricity. When all the cells work together, a large amount of electricity is produce and used to help the eel survive. This type of electricity is like static electricity, which builds up and then discharges. It does not flow continuously. Batteries Count Alessandro Volta was born in Como, Italy, into a noble family. The Italian physicist Alessandro Giuseppe Antonio Anastasio Volta was the inventor of the voltaic pile, the first electric battery. Voltaic Pile The first battery was created by Alessandro Volta in 1800. To create his battery, he made a stack by alternating layers of zinc, blotting paper soaked in salt water, and silver, like this: This arrangement was known as a voltaic pile. The top and bottom layers of the pile must be different metals. If you attach a wire to the top and bottom of the pile, you can measure a voltage and a current from the pile. The pile can be stacked as high as you like, and each layer will increase the voltage by a fixed amount.

Batteries : Dry Cells An electrochemical cell supplies a steady current. It is a collection of chemicals designed to produce small amounts of electricity. Batteries provide portable, convenient sources of energy for powering devices without wires or cables A dry cell is a common type of battery used today. Dry Cells The electricity-producing cells, that are referred to as 'batteries', are called dry cells. They are 'dry' because the chemicals used are in a paste. Batteries : Rechargeable Types of Rechargeable Batteries: nickel cadmium (NiCd), nickel metal hydride (NiMH), lithium ion (Li-ion), and lithium ion polymer (Li-ion polymer). Battery is discharged – battery is “dead”

Batteries : Wet Cells – Lead Acid A car battery (SLI Battery) typically has two ratings: CCA (Cold Cranking Amps) - The n umber of amps that the battery can produce at 0˚C for 30 seconds RC (Reserve Capacity) - The number of minutes that the battery can deliver 25 amps while keeping its voltage above 10.5 volts A deep cycle battery is designed to provide a steady amount of current over a long period of time. A deep cycle battery is also designed to be deeply discharged over and over again (something that would ruin a car battery very quickly). To accomplish this, a deep cycle battery uses thicker plates, spacing, and area for debris . Typical Battery voltage Dry Cells – D C AA AAA - 1.5 volts Ipod Batteries - about 3 volts (3.7) Quad or small motorcycle batteries - 6 volts Car or Truck Batteries - 12 volts Power cells In a fuel cell, the hydrogen and oxygen are separated by a membrane. The membrane captures the free electrons during the chemical reaction that forms water, which in turn powers anything hooked up to the fuel cell. It also releases some heat. Fuel cells are a remarkable power source. They store energy in two naturally occurring elements (oxygen and hydrogen, which are already in our atmosphere) and form a single waste product (pure water). Refueling a fuel cell means providing more hydrogen and oxygen. With an external source of electricity such as a solar panel, one can split the waste water back into its component parts and use it again as fuel! Or, as they did in the Apollo missions, you can drink the water.

Electrochemistry Humphrey Davy filled an entire room with 2000 cells to make one massive battery. His work led to a whole new field of science called electrochemistry, the study of chemical reactions involving electricity. Electrolysis Smaller batteries were used to split molecules into their elements, a process called electrolysis. Many industries use electrolysis to separate useful elements from solutions. Fuel for the Space Shuttle (to get pure oxygen and hydrogen ) Electroplating Silver and Gold plating can make jewelry and other attractive items look very expensive. The thin coating (which is usually stronger than the original element) is produced through a process called electroplating. This process is often used to protect the metal from corrosion. Anodizing Aluminum Anodizing is a process that coats aluminum parts with a layer of aluminum oxide, which is much harder than aluminum. It is used in products such as screen doors, airplanes, car parts, kitchenware and jewelry. Electro-refining Electro-refining is used to remove impurities from metal. Another process used by automobile companies bonds special paints onto car parts. Measuring Water Purity Pure water is not a good conductor of electricity. Conductivity is linked directly to the total dissolved solids Sea water's conductivity is one million times higher than that of deionized water. You can tell how pure water is by measuring it’s conductivity Electricity & Humans Automated External Defibrillator (AED’s) An automated external defibrillator (AED) is a portable electronic device that automatically diagnoses the life threatening cardiac arrhythmias of ventricular fibrillation and ventricular tachycardia in a patient, and is able to treat them through defibrillation, the application of electrical therapy which stops the arrhythmia, allowing the heart to reestablish an effective rhythm.

Pacemakers The pacemaker consists of two parts. The leads are wires with electrodes at the tip that transmit electrical signals to the heart muscle from the pulse generator. These electrical signals cause the heart muscle to contract (pump). The pacemaker is a small unit with a computer that generates the electrical signal. Most pacemaker implantations are performed under local anesthesia (similar to the anesthesia used by dentists). TASERS A Taser is an electroshock weapon sold by Taser International. It uses electrical current to disrupt voluntary control of muscles causing "neuromuscular incapacitation”. Someone struck by a Taser experiences stimulation of his or her sensory nerves and motor nerves, resulting in strong involuntary muscle contractions. Polygraph A polygraph (popularly referred to as a lie detector) measures and records several physiological indices such as blood pressure, pulse, respiration, and skin conductivity while the subject is asked and answers a series of questions. The belief underpinning the use of the polygraph is that deceptive answers will produce physiological responses that can be differentiated from those associated with non-deceptive answers.