Electroscope Used to are transferred to the and Foil becomes and

Transcription

1 Electricity Notes Chapter 17 Section 1: Electric Charge and Forces Electric charge is a variety of independent all with one single name. Electricity is related to, and both (-) and (+) carry a charge. Electric charge is an. All that contain, neutrons, and. An object can have a, or no charge. o Charge of proton o Charge of electron o Charge of neutron Atoms have because the charges of the and. Atoms become charged by. is a big spark that occurs when electrons move from one place to another very quickly because of the. can produce a force between the objects Objects are when their charges are different o Opposite charges charges they push apart o Like charges Electrons can be When different, electrons can be from one material to the other. The SI Unit of electric charge is the. Static Electricity - buildup of excess on an object o Excess on an object o Very short Static electricity is can cause it - charge may be transferred from object to object, but it cannot be or Opposite Charges, and like charge Why you end up with a static shock after walking across the carpet: o in the carpet more loosely than atoms in your shoes o Shoes from the carpet, becoming o Carpet & becomes o occurs when electrons are suddenly from one object to another- this appears as a spark Transfer of Electric Charge Different materials are can be to the other The direction depends on the material Conduction: o Electrons move more easily o well because: atoms in metals have through the material o Electrical conductors, such as copper wiring, allow electrons to move freely.

2 Insulation: o Insulator- a to move through it easily o Occurs because to the atoms in insulating materials like,, - the process of transferring charge by touching or rubbing two objects together - rearrangement of electrons on a neutral object by a nearby charged object We usually only notice static electricity in the. During the summer, the air is more humid. The water in the air helps electrons move off you more quickly, so you cannot build up as big a static charge. Electroscope Used to are transferred to the and Foil becomes and Electric Force & Field Electric force: the or on a charged particle that is. o Depends on and o Acts through a Electric field: the in which another charged object experiences an electric force. o Electric fields objects. o Any charged object that enters a region with an electric field. o Electric field Section 2: Current Voltage & Current An electric charge has that depends on its position in an electric field. o A that is close to has the potential to move away. o The 2 negative charges as a result of their. : difference in energy per as the charge moves between two points in the Higher, the can do. It is to consider than electrical potential energy. is the voltage difference in potential. o Also called This change occurs as a from one place to another in an. SI Unit for Potential difference is There is a Voltage across the. The potential difference or voltage across the two ends, or terminals, of a battery ranges from about for a small battery to about for a car battery. Most batteries are (or groups of connected cells) that convert into. Electrochemical cells contain o - a solution that conducts electricity, o - each a different conducting material.

3 What Is A Current? : the rate at which charge A, or individual negative charges. Made by electrons Electric Current - The flow of electrons through a wire or. Measured in units of Different from because it Charges flow from to push that causes charges to move For charges to, the wire must always, or circuit Ampere: A measure of moves through a wire in one second. The larger the, the capacity. There are two main kinds of electric current, o (DC) o (AC). o Explains how current gets moved Direct Current o (DC) Direct current is a. o From Alternating Current o (AC)-Alternating current is a, changing its many times in one second. ( / household) o Advantages of AC Voltage can More efficient over o From Generators o Used in your home o Transformers change Electrical Resistance - the tendency for a material to oppose the flow of electrons, changing electrical energy into and to the flow of charge All have some. Making,, or increases the As resistance increases current decreases!!!! Measured in : omega Ω Ohm s Law Ohm s law states that the is equal to the divided by the resistance I = V R The relationship among current, voltage, and resistance. I = Current V = Voltage R = Resistance

4 Practice Problems: Ohm s Law ( Resistance) 1. A car has a 12 volt system. The headlights are on a 10 amp circuit. How much resistance do they have? 2. Your house uses 120 volts. What amount of current would flow through a 20 ohm resistor? 3. A refrigerator s circuit has a current equal to A in it when the voltage across the circuit equals 116 V. What is the resistance of the circuit? 4. The resistance of a wire in a hair dryer is 7.7 Ω. If the current through the wire equals 15.6 A, what is the voltage across the terminals of the hair dryer? Conductors have. Insulators have. conduct under certain conditions. o materials that have electrical properties between those of insulators and conductors Some materials can become. Section 3: Circuits Circuits For current to flow there must be a : complete, a closed path through which electrons travel. Electrons flow from is done if there is a in the wire. - if any part of the circuit is, no current flows o Example- old style - A closed-loop path for electrons to flow through,. Resistance is. A resistor is a that uses electric energy to do work. A from the resistor to the completes the circuit. An open switch the. A is a model of an electric circuit with standard symbols for the electrical devices. Schematic Diagram Symbols Two Types of Circuits

5 : A circuit with only. o All the in a series circuit lie along a single path. o The in a series circuit is the at of the circuit. o Resistance in the if resistors are or. : The electrons in a parallel circuit can travel through, each path is separate. o If there s a in the circuit, through the other paths and maintain a complete circuit. o Parallel circuits in your home allow each light or appliance to to work. o A parallel circuit from when one of them stops working. Electric Power Electric Power is the is used in a circuit. When a charge moves in a circuit, it energy. This is transformed into useful work (like turning a motor) and is lost as. : The rate at which electricity does work or provides energy The amount of electric power a device uses to do work is determined by its resistance. P = V x I (P) power = (V) x (I) in the circuit. Electrical power is expressed in P ( ) = V ( ) x I ( ) Practice Problems: Electrical Power 1. An electric mixer draws W of power. If the mixer is plugged into an outlet across a voltage of 115 V, what current is in the mixer s circuit? 2. A nightlight uses 4.00 W of power when plugged into an outlet. Assume that the only resistance in the circuit is provided by the light bulb s filament. The current in the circuit is 3.40 x 10-2 A. What is the voltage across the filament? 3. A current of 5.83 A is used to produce the microwave radiation in a microwave oven. If the voltage

6 across the oven is 120 V, how much power does the use? 4. A refrigerators uses a current of 0.62 A and a voltage of 116 V. How much power does the refrigerator use? Electric safety Fuses and circuit breakers. - contain a small piece of metal that melts if the current becomes too high, opening the circuit and stopping the flow of current - contain a small that bends when it gets hot, opening the circuit and stopping the current o Circuit breakers are often. or can cause electric appliances to short-circuit. A short circuit occurs when electricity takes a and in the circuit. Because of this the resistance of the circuit is less and the. The can produce enough and start a fire, or cause