* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Notes electrical current new
Survey
Document related concepts
Transcript
I. Electrical circuits a. Electrical current is the flow of charge, either electrons or ions, through matter i. electrons have a negative charge, in materials that are able to conduct electricity, electrons are free to flow ii. ions are molecules with a charge, ions are able to pass a charge through a material b. Law of Electric Charges i. Electric force - all charged objects exert an electric force on each other ii. Opposite charges are attracted iii. Like charges repel iv. Electric field - space around a charge which exerts a force 1. Any spinning or moving electron has an electric field 2. Electric fields may surround any material c. Voltage i. Voltage is electric push, measure of how much electrical energy a source can provide. ii. To move electrons we need a force or push which is called voltage or potential difference. iii. Potential difference – the difference in electric potential (voltage) between two points. Free charge flows when there is a difference, and will continue until both points reach a common potential iv. Push needed to move an electron from one place to another v. Measured in volts vi. Source of Electricity (Battery) 1. Supplies potential energy to a circuit 2. Sets the voltage for the circuit d. Current i. Current is the rate of flow of charge ii. Amperes – flow electrical charge past a point per second iii. Often shortened to amps iv. Symbol for ampere is A v. In equations, the symbol for current is I e. Resistance i. Resistance is the opposition to the flow of electrons by the atoms of the material ii. Measured in ohms iii. Ohms – the SI unit of electric resistance. One ohm is the resistance of a device that draws a current of one ampere when a voltage of one volt is impressed across it. II. f. Electric circuit i. There must be a complete path for electricity to follow and a voltage difference ii. Circuit is a closed conducting pathway for electrons to flow through iii. Simple circuits must have 1. a source of electricity “battery” 2. conductor “wire” 3. load “light bulb or motor” what the electrons do work on iv. There are two types of circuits 1. Series circuits - a circuit that has only a single path (one loop) for current to flow through all of its parts. a. Total voltage is divided, equal to the sum of all the voltage b. Total resistance is equal to the sum of all the resistors c. Current stays the same 2. Parallel circuits - requires more than one path for current flow in order to reach all of the circuit parts. a. Current is divided, total current is equal to the sum of all the currents b. Voltage stays the same c. The combined resistance is less than the smallest resistance in the circuit Electrical Symbols Source Voltmeter Bulb Ammeter Motor Resistance Switch on Fuse Switch off Ohm’s Law a. Ohm’s Law – relationship between current, voltage, and resistance b. Current equals voltage divided by resistance i. I = V/R ii. R = V/I iii. V = I x R iv. Problems 1. What is the resistance of an electric frying pan that draws 12 amperes of current when connected to a 120-volt circuit? 2. How much current is drawn by a lamp that has a resistance of 100 ohms when a voltage of 50 volts is impressed across it? 3. What is the voltage for a 12 ohms vacuum that uses 10 amps of current?