Presentation on theme: "Chapter 16 Electric Forces and Fields Section 1. Electricity Static Electricity- a buildup of electrons - Ex: sliding your feet across the carpet Current."— Presentation transcript:
Electricity Static Electricity- a buildup of electrons - Ex: sliding your feet across the carpet Current Electricity- flow of electrons - Ex: car battery
Electric Charge Electric Charge- electrical property of matter that creates electric and magnetic forces and interactions There are two kinds of electric charge - Positive Charge - Negative Charge Like charges repel Unlike charges attract
Electric Charge cont’d Electric charge is conserved Example: When a balloon is rubbed against your hair, electrons are transferred to the balloon. Your hair becomes positive and the balloon gains a negative charge
Electric Charge Atoms consist of protons, electrons, and neutrons Unit of electric charge: Coulomb, C Mass of proton: +1.6 x 10^-19 Mass of electron: -1.6 x 10^-19
Transfer of Electric Charge Charging by friction: - one material gains electrons and becomes negatively charged while the other loses electrons and becomes positively charged Ex: sliding your feet across the carpet
Transfer of Electric Charge Charge by contact: When a negatively charged object touches a neutral object. Electrons flow from the rod to the doorknob. The doorknob now has a negative charge.
Transfer of Electric Charge Induced charge: A negatively charged rod is brought near a neutral doorknob. The charges on the doorknob will redistribute themselves.
Transfer of Electric Charge Electrical conductors- a material in which charges can move freely - Ex: copper, aluminum Electrical insulators- a material in which charges cannot move freely - Ex: glass, rubber, silk, plastic
Transfer of Electric Charge Semiconductors- have electrical properties between insulators and conductors Superconductors- have zero electrical resistance; can conduct electricity indefinitely without heating
Electric Force Electric force- the force of attraction or repulsion between objects due to charge Depends on charge and distance
Electric Force Electric Field- a region in space around a charged object that causes a stationary charged object to experience an electric force
Current Electrical Potential Energy- the ability to move an electric charge from one point to another The electrical potential energy between two negative charges decreases as the distance between them increases.
Current Potential Difference- the work that must be done against electric forces to move a unit charge from one point to the other SI unit: volt, V a.k.a voltage
Current Current- the rate that electric charges move through a conductor SI unit: ampere, A (amp)
Electrical Resistance Resistance- the opposition posed by a material or a device to the flow of current Caused by internal friction, which slows the movement of charges through a conducting material.
Electrical Resistance SI unit of resistance: ohm, Ω Equation: resistance = voltage R = V current I
Example A nine volt battery supplies power to a cordless curling iron with a resistance of 18 ohms. How much current is flowing through the curling iron?
Example A 110 volt wall outlet supplies power to a strobe light with a resistance of 2200 ohms. How much current is flowing through the strobe light?
Example A CD player with a resistance of 40 ohms has a current of 0.1 amps flowing through it. Sketch the circuit diagram and calculate how many volts supply the CD player?
Circuits Electric Circuit- a set of electrical components connected such that they provide one or more complete paths for the movement of charges. An electric circuit is a path through which charges can be conducted
Circuits Closed Circuit- this is the conducting path produced when (for example) a light bulb is connected across a battery’s terminals Open Circuit- results when there is no complete path, this means there is no charge flow and no current
Circuits Switch- used to open and close a circuit - Ex: Light switch in your home Schematic Diagram- a diagram that depicts the construction of an electrical circuit or apparatus
Circuits Series- the components of a circuit that form a single path for current Parallel- a circuit in which all of the components are connected to each other side by side
Circuits Electrical Energy- the energy that is associated with charged particles because of their positions Electric Power is the rate at which electrical energy is used in a circuit
Circuits Electric Power Equation: Power = current x voltage or P = IV SI unit: watt, W
Circuits Example: When a hair dryer is plugged into a 120 V outlet, it has a 9.1 A current in it. What is the hair dryer’s power rating?
Circuits Fuse- an electrical device that contains a metal strip that melts when current in the circuit becomes too great Fuses “blow out” when the current in the circuit reaches a certain level
Circuits Circuit Breaker- a switch that opens a circuit automatically when the current exceeds a certain value When the current exceeds a certain level the circuit breaker acts as a switch and opens the circuit. These can be reset unlike fuses.