Electricity PPT PDF

Electricity Here is where your presentation begins Electrostatics Electrostatics- The study of the effects of Stationary charges on each other and their surroundings. Electrostatics focuses on the charges within objects rather than a moving stream of electricity. Electrical Force- The attractive...

Electricity Here is where your presentation begins Electrostatics Electrostatics- The study of the effects of Stationary charges on each other and their surroundings. Electrostatics focuses on the charges within objects rather than a moving stream of electricity. Electrical Force- The attractive or repulsive interaction between two charged objects. - Interaction between ions (charged particles) - ions are created by adding or removing elections Parts of the Atom -Protons, electrons, neutrons -What are they and how are they created? Electrostatics Fundamental Rule of Electric Charge 1. -opposite charges attract, similar charges repel Electrostatics Electrical Charge- An unbalance between electrons and protons - symbol “q” -Unit: Coulomb “C” - charges are always whole numbers and can’t be divided -charge is always conserved Electron Charge: C Proton Charge: C Neutron Charge: 0C Electrostatics Conductor- material that allows electrical charge to flow easily through the material - Have free moving electrons -ex: metals (gold, silver, copper) Insulator- material that does not allow electrical charge to flow easily through the material -ex: wood, plastic, rubber Electrostatics Semi- conductor- a material that is usually an insulator, but due to impurities acts like a conductor -ex: silicon, germanium Super-conductor- a material that has no resistance to the flow of electric charge - usually occurs at absolute zero -colder temperatures allow for a greater flow of charge Electrostatics 3 ways to charge an object - Friction - How: Rubbing 2 surfaces together transferring electrons - created a positive and negative side -ex: clothes in dryer, scooting feet along carpet -Conduction - How: transferring static charge through direct contact -neutral object then has the same charge as the original object -the 2 objects repel each other because they have the same charge -the charge becomes permanent -Induction -How: placing a charged object next to object without touching Electrostatics Friction Electrostatics Lightning - massive release of electrostatic charge -a form of static charge through induction - lightning starts as a negative charge in the clouds, the negative pushes the negative in the ground away, leaving positive charges, which then attract the negative charges Electrostatics Grounding -the process of touching an object that is directly connected to the ground - the ground is the ultimate storage of charge - charge spreads and weakens over a large area -typically used with appliances because they build up a lot of static charge. Electrostatics Coulombs law: - describes the electrical force between two objects - Coulombs law states that as the charge of an objects increases, the force (either attractive or repulsive) will increase, if the charge of the objects decrease, the force will decrease. -As the distance between two objects increases, the electric force will decrease, as the distance between the object decreases, the electric force increases. : Electric Force (newtons “N”) : charge of one object (coulombs “C”) : charge of the other object (coulombs “C”) r: distance between center of the two objects (meters “m”) K: Coulombs constant ( N*/) Electrostatics What is a NEWTON????? A newton is the amount of force required to accelerate 1Kg of mass 1m/. 1N: 1 What is a Coulomb???? A coulomb is the electricity conveyed in one second by a current of one ampere. 1C: 1A*s : Electric Force (newtons “N”) : charge of one object (coulombs “C”) : charge of the other object (coulombs “C”) r: distance between center of the two objects (meters “m”) K: Coulombs constant ( N*/) Electrostatics Using Coulombs Law: 1. Determine information Given 2. Determine what variable you are solving for 3. solve for the given variable 4. determine the units for your answer 5. Determine if the electric force is attractive or repulsive Attractive or repulsive??? - electric force is based on - distance and K are always positive - if the electric force is positive, it is repulsive - same sign - If the EF is negative, the force is attractive -opposite signs Electrostatics What is the electric force between two objects that both have a charge of.50C and the distance between the objects is 2.5m? Is the force attractive or repulsive? Electrostatics If an object attracts another object with an electric force of -500N, what is the charge of the second object if the first object has a charge of.001C and the two objects are 8m apart? Electrostatics What is the electrical force between two objects, one with a charge of -.21C and the other with a charge of.78C, I the two objects are.050m apart? Is the force attractive or repulsive? Electrostatics Law of ones Because coulombs law is mathematically the same as universal gravitation, we can predict the change in the electrical field when the charge and the distance between the charges changes. THIS DOES NOT GIVE YOU THE FORCE JUST THE AMOUNT IN WHICH IT WILL CHANGE Electrostatics Law of ones: how do we use it???? 1.start with the formula for coulombs law: 2.Place a 1 for any variable that is NOT changing (K will always be 1 because it is a constant) 3. Plug in a number in any variable that is changing that represents the change. (ex. Doubling:2, half:1/2) Electrostatics Law of ones: how do we use it???? 4. Solve the right side of the formula using the ones and the number values for change. 5. The number represents the change in the electric force between two objects. *change in charge will directly affect the Electric force. *change in distance is squared and will have an inverse effect on the Electric force Electrostatics Law of ones: how do we use it???? If an electric force (EF) exists between two objects, and the charge of one of the objects is tripled, what will happen to the electric force between the two objects? Electrostatics Law of ones: how do we use it???? If an electric force exists between two objects, and the charge of one of the objects becomes 5 times greater, what will happen to the electric force between two objects? Electrostatics Law of ones: how do we use it???? If an electric force exists between two objects, and the distance between the two objects is doubled, what will happen to the electric force between the two objects? Electrostatics Law of ones: how do we use it???? If an electric force exists between two objects, and the charge of one of the objects is doubled, and the distance between the two objects is doubled, what will happen to the electric force between the two objects? Electrostatics Law of ones: how do we use it???? If an electric force exists between two objects, and the distance between the objects decreased to 1/3 of the original distance, what will happen to the electric force between the two objects? Electrostatics Can you draw magnetic field lines? -Using a magnet and a compass, try and draw a magnetic field around a magnet. 1. draw the field around a single bar magnet 2. draw the field around a horseshoe magnet 3. draw the field around two bar magnets next to each other Electrostatics Electric field- a field that illustrates the electric force created by an electrostatic charge. - Can either show isolated charges or groups of 2 or more charges. -electric fields help us predict interactions between charged particles. Electrostatics How to draw electric fields: Rule 1: electric field lines will never cross! Electrostatics How to draw electric fields: Rule 2: electric force is drawn as a vector (has magnitude and direction) with an arrow in the direction of the electric force Electrostatics How to draw electric fields: Rule 3: Electric force is always drawn coming out of a positive charge and going to a negative charge Electrostatics How to draw electric fields: Rule 4: Positive electric charges will combine with negative charges, the arrow will show the direction of the attraction in the middle of the field Electrostatics How to draw electric fields: Rule 5: Electric field lines coming out of a positive will repel from electric field lines coming from another positive Electrostatics How to draw electric fields: Rule 6: Strong electric fields have a higher density (in the same space) of arrows and the arrows are longer in distance. Weak Strong Electrostatics Rule 7: Show all electric field lines even those that are not connecting Electrostatics Practice: Draw an electric field diagram for an 2 isolated charged objects, one with a strong positive charge and one with a weak positive charge. Electrostatics Practice: Draw an electric field diagram for an 2 isolated charged objects, one with a weak positive charge and one with a weak negative charge. What is the difference between the two? Electrostatics Practice: Draw an electric field diagram between two charged objects, both with a weak positive charge. Electrostatics Electric Field potential: - - An electric field shows how electric force affects all the objects around it and based on the location in the electric field, the object will experience a greater attraction or repulsion. - - The Electric field potential is the objects ability to be affected by an electrical force - - This electric potential is called Voltage. Electrostatics Voltage: - - Voltage (V) is the amount of electric potential that an object has based on the location of the object within the electric field - - Stronger electric field = Larger voltage - - Voltage (V)= J/C - 1joule:1kg* vs. 1Newton: 1kg*m Electrostatics Current: - - Electric current is a continuous flow of electric charge (electrons) through a material - - electric current is created when there is a difference in potential energy between two points - - Each point within an electric field will have a different potential energy (PE) based on the distance between the point and the field. Electrostatics What is Potential Energy???? Potential energy is energy that is stored. This is the energy before an object is in motion Electrostatics Voltage - -The electric potential (pressure) on a charge to keep it at a certain position. - - Electric Current will always flow from a point of high voltage to low voltage until they have reached the same voltage - - Is there an electric current when both points have the same voltage? Electrostatics Voltage Source - -A voltage source creates a continuous difference in voltage between two points so there is a continuous current. - - Can you think of any voltage sources??? - - What is a home outlet voltage difference??? Electrostatics Voltage Source Generator: uses mechanical energy or kinetic energy to do work to create voltage. What is kinetic energy??? The energy an object has in motion. Ex of generators: windmill, hydroelectric plant, hand crank generator, coal plant Electrostatics Voltage Source Photocells: converts light energy into electrical energy or electric potential (voltage) Example: Solar panel Electrostatics Voltage Source Batteries: convert chemical energy to electric potential (V) What is chemical energy??? Dry cell: reaction is powder or paste based -lower risk of leaking - most can’t be recharged -ex: Duracell battery Wet Cell: reaction is liquid based - higher risk of leaking -can be recharged -ex. Car battery Electrostatics Voltage Source Batteries: 3 kinds -Primary use and throw away (not rechargeable) -Secondary rechargeable uses a chemical reaction to recreate the electric current -Fuel Cell continuously pumps in chemical for a reaction Electrostatics Current: Variable for Current: “I” Units for current is or Ampere (Amps) Electrostatics Direct Current (DC) Alternating Current (AC) - -Current flows in one - -Current flows in one direction direction and then - -ex: battery flows in the opposite direction - -ex: outlets in a house Current always flows from positive to negative Electrostatics How do we manage current???? -High electric current creates a large amount of friction, which creates heat, which could start a fire. - What is Friction again????? Electrostatics How do we manage current???? Fuses: How does a fuse work??? Electrostatics How do we manage current???? Fuses: How does a fuse work??? A fuse is a piece of metal that melts at a high temperature when there is a high electric current. Electrostatics How do we manage current???? Fuses: How does a fuse work??? A fuse is a piece of metal that melts at a high temperature when there is a high electric current. Does a fuse have to be replaced??? Electrostatics How do we manage current???? Fuses: How does a fuse work??? A fuse is a piece of metal that melts at a high temperature when there is a high electric current. Does a fuse have to be replaced??? Yes, when a fuse melts it can no longer complete the circuit Electrostatics How do we manage current???? Breakers: What is a circuit breaker?? Electrostatics How do we manage current???? Breakers: What is a circuit breaker?? a circuit breaker detects low or high voltage and shuts off the current before any damage can be done. Electrostatics How do we manage current???? Breakers: What is a circuit breaker?? a circuit breaker detects low or high voltage and shuts off the current before any damage can be done. Do breakers have to be replaced???? Electrostatics How do we manage current???? Breakers: What is a circuit breaker?? a circuit breaker detects low or high voltage and shuts off the current before any damage can be done. Do breakers have to be replaced???? No, because the breaker is able to detect voltage highs and lows, it shuts the flow of electrons off before anything happens Electrostatics Resistance: Resistance is the material that restricts the flow of electric current (electrons) Resistance (R) is measured in Ohms Ω. Ohm: 1J*s Electrostatics Resistance: 4 factors affect resistance: 1. 1. Conductivity: more conductivity = less resistance 2. 2. Length: longer the material = further the current has to travel = more resistance 3. 3. Thickness: thicker material= less resistance b/c there is more material for the current to travel through 4. 4. Temperature: hotter = more resistance Electrostatics Ohms Law: - Discovered by Georg Ohm - Relates Voltage(V) to current(I) and electrical resistance(R) Electrostatics Ohms Law: Variables: Voltage (V) : Volts : V Current (I): Amperes (amps) : A Resistance (R): Ohms : Ω Electrostatics Ohms Law: What voltage is needed to run a current of 0.5A through a metal wire with a resistance of 10,000Ω? Electrostatics Ohms Law: If a battery creates an electric current of 15V and runs through a wire with a resistance of 125Ω, what is the electric current created? Electrostatics Ohms Law: If a generator creates a voltage of 150V to create a current of 0.02A, what is the resistance of the generator? Electrostatics Electric Current: A voltage source creates a force that moves an electric current over a distance. Work: That force it takes to move current a certain distance Work-Energy Theorem- all work is derived from kinetic energy Work = F*d or Work = force * distance Electrostatics Current: To create the current, work has to be done to move electrons Power: Work done over a period of time Power = or P = or P= Power is measured in Watts(W) Electrostatics Current: To create the current, work has to be done to move electrons Force of EC is based on charge (q) Distance of EC is based on Voltage (V) P= Electrostatics Power: What power is needed to create an electric current of.17A if the needed voltage from the power source is 225V? Electrostatics Power: If a generator uses a power of 500W and creates a voltage of 800V, what is the current in the generator? Electrostatics Power: A 750watt hair dryer is used at a 120V outlet, what was the current of the hair dryer? Electrostatics Power: A 750watt hair dryer is used for 180s, how much work was done by the hair dryer? Electrostatics Power: The power rating for a dishwasher is 1200watts, the typical cycle for the dishwasher is 60 minutes, how much work was done by the dishwasher? Electrostatics Honors Power: A student who weighs 500N climbed the stairs from the first floor to the third floor, 15 meters above, in 20s. How much work did they do? What was her power? Electrostatics Honors Power: The power rating of an electric lawn mower is 2000Watts. If the lawn mower is used for 120s and goes 10m, how much force was exerted? Electrostatics Honors Power: The power rating of an electric lawn mower is 2000Watts. If the lawn mower is used for 120s and goes 10m, how much force was exerted? Electrostatics Power companies: What do power companies sell??? Electrostatics Power companies: What do power companies sell??? Power companies sell energy, not power, not electrons. They are selling the energy needed to push the electrons that are already in the electrical lines to create the alternating current. Energy is measured in Watts* seconds (W*s) or Joules These are really small measurements so energy is Electrostatics Power companies: What do power companies sell??? Power companies sell energy, not power, not electrons. They are selling the energy needed to push the electrons that are already in the electrical lines to create the alternating current. Energy is measured in Watts* seconds (W*s) or Joules These are really small measurements so energy is Electrostatics Power companies: Power companies always sell energy as a rate ($) per kilowatt hour. Cost of electricity = rate ($/kWhr) * Energy used (kWhr) Electrostatics Power companies: Power company activity Electromagnets Magnetism: The property of a substance to create a magnetic force (based on the creation of a magnetic field) Magnets are considered dipoles (having 2 poles) Magnets have a north and a south pole Electromagnets Types of magnets: 1. Permanent- these substances when placed in a magnetic field will be permanently be magnetized 2. Temporary- these substances will act like magnets in a magnetic field, but will quickly lose their magnetism when removed from the magnetic field. Electromagnets Magnetism: Magnetic poles are very similar to electric charges: 1. Magnetic poles can act over a distance 2. Opposite poles attract where similar poles will repel. North + North : Repel South + South: Repel North + South: Attract Electromagnets Magnetism: Unlike charges, magnetic poles can not be separated. When magnets break, they create smaller magnets. Electromagnets Magnetic Field: The space around a magnet where magnetic force is exerted. More lines = stronger field Lines travel away from the north pole Lines travel toward the south pole Always strongest near the poles Electromagnets Compass: When a compass is placed in earths magnetic field: - A bar magnet will align so that its north seeking pole faces geographic north - A bar magnet will align itself so that its south seeking pole faces geographic south. Electromagnets Electromagnets Earth: Earth is a large magnet. The inner core is made of molten (liquid) iron and nickel. The iron and nickel are constantly moving creating a constant magnetic field When solar winds hit the magnetic field, it created the light shows known as the southern and northern lights. Electromagnets Earth: Northern Lights (Aurora Borealis) Southern Lights (Aurora Australis) https://www.youtube.com/watch?v=fVsONlc3OUY Electromagnets Electromagnets All metals are good conductors of electricity Only some metals are good conductors of magnetism Electromagnets Electromagnets An electric current will create a magnetic field perpendicular to the direction of the electric current. When the flow of electric current is switched, the poles in the magnetic field switch as well. Electromagnets Electromagnets All atoms have electrons that spin and they spin in opposite directions. Most atoms have the same number of electrons spinning in both directions canceling out so there is no magnetic field Iron (Fe), Nickel (Ni)l, and Cobalt (Co) have an uneven number of electrons spinning in both directions. Electromagnets Electromagnets The electrons in the iron are spinning and creating an electric current and magnetic field. The domains are not lined up though, this means the magnetic field is weak and spread out in all different directions. A magnet lines up all the domains in the iron and creates a permanent magnet. Electromagnets Electromagnets Magnets can be demagnetized by dropping or heating the magnet. Michael Faraday discovered electromagnetic induction. Electromagnetic induction- an electric current will always create a magnetic field around the wire. Electromagnets Electromagnets Whenever a electric current runs through a wire, it creates a magnetic field. We can create a magnet by simply running an electric current through a length of wire. The magnetic field created by an electric current always travels around the wire in a perpendicular pattern (90 degrees) Electromagnets Electromagnets An electromagnet is created by running an electric current through an insulated wire, which is wrapped around a material (typically iron) The magnetic field is collected in the iron core and this creates a strong magnetic field. Electromagnets Electromagnets 3 Factors Affect the strength of the electromagnet: 1. The number of loops in the wire - the more loops, the stronger the electromagnet 2. The amount of current running through the wire - stronger the current the stronger the electromagnet. 3. The material of the core - Iron and nickel create strong electromagnets Electromagnets Electromagnets 3 Factors Affect the strength of the electromagnet: 1. The number of loops in the wire - the more loops, the stronger the electromagnet 2. The amount of current running through the wire - stronger the current the stronger the electromagnet. 3. The material of the core - Iron and nickel create strong electromagnets Electromagnets Electromagnetic Induction If you move a magnet through the center of coil wires, the magnet will create a magnetic field within the wires, creating a magnetic force on the electrons within the wires, forcing them to move, creating electric current. Electromagnets Electromagnetic Induction 2 ways to use electromagnetic induction: Electric motor: converts electrical current to mechanical energy Electric Generator: mechanical energy to electricity Electromagnets Electromagnetic Induction Transformers: a device that can increase or decrease the voltage of electric current using electromagnetic induction Why do we need transformers? - Carry current ling distances - Low voltage would require to much power to carry the current - High voltage would damage electronics in the Electromagnets Electromagnetic Induction Transformers A transformer is made of an iron core with two series of coils wrapped around different sides of the transformer. - Primary Coil = input - Secondary Coil = output - The current on the output side will depend in if there are more or less coils in the secondary set of coils Electromagnets Electromagnetic Induction Transformers Step Up: secondary coil has more coils than primary and the voltage output is greater Step Down: secondary coil has less coils than primary and the voltage output is less. Electromagnets Electromagnetic Induction Transformers Faradays Law: the change in loops between the primary and secondary coil in a transformer is directly related to the change in voltage between the coils in a transformer. : Voltage of primary coil : Voltage of secondary coil : Number of loops in primary coil : Number of loops in secondary coil Circuits 3 things needed for a circuit: 1.Circuit must be closed -closed circuit: current has a complete path to follow -open circuit: open point that looses current 2. Voltage difference must exist 3. Must be a voltage pump to maintain the voltage difference Circuits Two Types of circuits: Series: a circuit where all devices are aligned in a single path so the current flows continuously through all devices V= I= R= Circuits Two Types of circuits: Series: a circuit where all devices are aligned in a single path so the current flows continuously through all devices When you add a device to a series circuit: Voltage across each device decreases and the total voltage stays the same Current always remains the same Circuits Two Types of circuits: Parallel: a circuit where each device is directly attached to the voltage source V= I= = Circuits Two Types of circuits: Parallel: a circuit where each device is directly attached to the voltage source When you add a device in a parallel circuit: Total voltage and voltage of the devices remains the same Total current increases with each device added Total resistance decreases with more electronic devices Circuits Parts of a circuit: Battery: two lines on a diagram: long is positive, short is negative Resistor: jagged line: slows down the current Circuits Circuits: We can use ohms law to determine the unknown variable: It can only be used at the same point: Ie) or NOT: Circuits Circuits: We can use ohms law to determine the unknown variable: It can only be used at the same point: Ie) or NOT: