Bell work Electric Charge Write a definition of this word in your own terms/words. Use an old textbook to finish the study guide.

Cancasci Notes

Electricity from Magnetism IAN 9-9

Electric current from a Magnetic field An electric current is only produced when the magnetic field is changing. Electromagnetic induction is the process of producing an electric current by changing the magnetic field.

Electric current can be produced in two ways… Moving a magnet within a coil of wire Moving wire between poles of a magnet An electric current is induced only when a wire cuts through/crosses the magnetic field lines.

Applications of Electromagnetic induction A generator is a device that uses electromagnetic induction to convert kinetic energy into electrical energy.

Generators produce alternating current-electrical current that continually changes direction.

Producing electricity for your home In most large scale generators the magnet is turned inside the coil of wire. Several methods are used for turning the turbine, that turns the magnet. Thermal energy, burning something (coal), to turn water into steam to turn the turbine. Water-kinetic energy of moving water to turn the turbine Wind-Kinetic energy of wind to turn the turbine

Once the turbine is turning it turns the magnet inside the coil of wire, inducing an electric current and generating electricial energy.

Getting the electricity to your home You do not have to write down this slide Electrical energy generated at a power plant is too high of a voltage to use in your home. Plus most homes are too far away from these plants. If the energy was supplied through wire to your home most would be lost as thermal energy before it reached your home. You need to increase the voltage even more!

Getting the electricity to your home A transformer increases or decreases the voltage of an alternating current. Simple transformers consist of wires wrapped around an iron ring.

Getting the electricity to your home Alternating current from an electrical energy source is supplied to one coil, called the primary coil. The changing magnetic field in the iron ring induces an electric current in the other coil, called the secondary coil. The number of loops on each side of the transformer determines if it is a step-up or step down transformer.

Getting the electricity to your home If it increases the voltage, it is a step-up transformer. If it decreases the voltage, it is a step-down transformer.

Electric Charge and Static Electricity IAN 9-11

Electric Charge Charges Exert Force Atoms are composed of particles with electric charge. The law of electric charges states that like charges repel and opposite charges attract.

Electric Charge, continued The Force Between Protons and Electrons Because protons and electrons have opposite charges, they are attracted to each other. The Electric Force and the Electric Field The force between charged objects is an electric force. An electric field is the region around a charged object in which an electric force is exerted on another charged object.

Charge It! Friction Charging by friction happens when electrons are “wiped” from one object onto another. Conduction Charging by conduction happens when electrons move from one object to another by direct contact. Induction Charging by induction happens when charges in an uncharged metal object are rearranged without direct contact with a charged object.

Charge It!, continued Conservation of Charge When you charge something by any method, no charges are created or destroyed. The numbers of electrons and protons stay the same. Detecting Charge You can use a device called an electroscope to see if something is charged.

Moving Charges Conductors An electrical conductor is a material in which charges can move easily. Insulators An electrical insulator is a material in which charges cannot move easily.

Static electricity is the electric charge at rest on an object. Electric Discharge The loss of static electricity as charges move off an object is called electric discharge.

Electric Current and Electrical Energy IAN 9-13

Electric Current Electric current is the rate at which charges pass through a given point. Electric current is expressed in units called amperes, or amps. Making Charges Move When you flip a switch, an electric field is set up in the wire at the speed of light. The electric field causes the free electrons in the wire to move.

Electric Current, continued Commanding Electrons to Move This electric field is created so quickly that all electrons start moving through the wire at the same instant. Think of the electric field as a command to the electrons to charge ahead.

Direct current flows in one direction Electric Current, continued AC and DC There are two kinds of electric current—direct current (DC) and alternating current (AC). Direct current flows in one direction Alternating current alternates direction

The higher the voltage, the more charge is moved between two points. Voltage is the potential difference between two points in a circuit. Voltage is expressed in volts (V). Voltage and Energy Voltage is a measure of how much force is present to move electrons (charge) between two points. Think of voltage as pressure in a water pipe that makes water flow when you turn on the tap. The higher the voltage, the more charge is moved between two points.

Voltage, continued Voltage and Electric Current As long as there is a voltage between two points on a wire, charge will flow in the wire. The amount of the current depends on the voltage. Varying Nature of Voltage Different devices need different levels of voltage.

Resistance is the opposition to the flow of electric charge. Resistance and Material Good conductors, such as copper, have low resistance. Poor conductors, such as iron, have higher resistance. Resistance, Thickness, and Length Thick, short wires have less resistance than thin, long wires.

Resistance, continued Resistance and Temperature In general, the resistance of metals increases as temperature rises.

Factors That Affect Resistance Click below to watch the Visual Concept. Visual Concept

Generating Electrical Energy Parts of a Cell A cell contains a mixture of chemicals called an electrolyte. Every cell also has a pair of electrodes made from conducting materials. Kinds of Cells Two kinds of cells are wet cells and dry cells. The electrolytes in dry cells are solid or paste-like.

Photocells A photocell converts light energy into electrical energy. Generating Electrical Energy, continued Thermocouples Thermal energy heat can be converted into electrical energy by a thermocouple. Photocells A photocell converts light energy into electrical energy.