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Ch 17/18 Electricity & Magnetism. Electric Charge:. Electric charge – a property of matter that creates electric and magnetic forces and interactions. - can have a negative charge (-). - can have a positive charge (+). - can no charge (neutral). Electric Charge:. - Like charges repel.
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Electric Charge: • Electric charge – a property of matter that creates electric and magnetic forces and interactions. - can have a negative charge (-) - can have a positive charge (+) - can no charge (neutral)
Electric Charge: - Like charges repel - Opposite charges attract
Imbalance of protons and electrons • electric charge depends on an imbalance of protons and electrons. • objects that lose electrons become positively charged. • objects that gain electrons become negatively charged.
Transfer of electric charge • when different materials are brought together electrons can be moved from one object to the other.
Flow of electrons • Conductor– something that allows the flow of electrons Ex. • Insulator– something that normally doesn’t allow theflow of electrons Ex.
Charging objects: • Can charge an object by gaining or losing electrons
Charging objects: 1. Friction – Rubbing two materials against each other. • Ways for charging to happen: - one becomes negatively charged and one becomes positively charged.
Charging objects: • Ways for charging to happen: 2. Contact – electrons move when you touch something
Inducing a Charge • When a neutral object is forced to show a charge. • when a charged object comes near a neutral object it can cause the particles to arrange themselves so that the negative charges are arranged to be near the charged object, resulting in one part of the object having a positive charge and one part with a negative charge.
Electric Force • attraction or repulsion between charged objects
Electric Force • 2 variables affect the amount of electric force. 1. Amount of charge - strong charge = strong force 2. Distance - closer the items = stronger force
Electric Field • area around a charged object where another object experiences the electric field
Electric Field • Can draw electric field lines to show the direction of an electric field and the strength of the charged object
Electric Currents • Electric Potential Energy • the PE of a charged particle due to its position in an electric field. • High PE when electrons are close • Low PE when electrons spread out
Voltage (volts) • Measurement of potential difference. - the change in electric PE of a charged particle divided by its charge.
Current • the rate that the electric charges move through a given point (ex. a wire) • SI unit for current is ampere (A) 1 A = 1C/s - 1C = 6.25 x 1018 electrons
Sources of electric current – • device that is a source of electric current because of the potential difference between terminals. - ex.
2 types of electric current • 1. DC current • direct current - moves in one direction - ex.
2 types of electric current • 2. AC current • alternating current - moves back and forth - ex.
Resistance • ratio of the voltage across a conductor to the current it carries. • R = voltage/current V/I SI unit = ohms (_______)
Resistance • occurs because of friction between the electrons in the current and the material in the conductor. • this friction causes heat and slowing the electrons
Resistance • amount of resistance is based on three variables a. temperature - colder = low resistance - hot = high resistance
Resistance • amount of resistance is based on three variables b. Length - shorter = low resistance - longer = high resistance
Resistance • amount of resistance is based on three variables c. thickness - thicker = low resistance - thinner = high resistance
Circuits • electric circuit - a device that creates a path for electric current to pass through. • need a complete circuit for electrons to pass through http://phet.colorado.edu/en/simulation/circuit-construction-kit-ac-virtual-lab
Circuits • closed circuit (no gap) = electricity • - open circuit ( a gap in circuit) = no electricity • - switch = device to open or close a circuit • - fuse = a device that prevents an overload of current
Closed vs. Open Circuit • Closed circuit • Open circuit
Circuits • Two types of circuits • 1. series circuit - everything lined up on one circuit • 2. parallel circuit - items lined up on parallel circuits