Current Electricity What is Current Electricity? Electrical Circuits Electrochemical Cells Wet, Dry and Fuel Cells WB – What is static electricity - What is current electricity To operate electrical device you need a continuous flow of electrons = current electricity How is current electricity different from Static electricity Current electricty is the flow of electrons in a circuit through a conductor Static electriciy is the electric sharge that builds up on the surface of an object Discharges when given a path but does not have continuous flow

Current Electricity Current Electricity – continuous flow of electrons in a closed circuit A flow of electrons moves continuously as long as there is: An energy source A complete path To operate electrical device you need a continuous flow of electrons = current electricity How is current electricity different from Static electricity Current electricty is the flow of electrons in a circuit through a conductor Static electriciy is the electric sharge that builds up on the surface of an object Discharges when given a path but does not have continuous flow

Electrons flow from negative to positive Electrical Circuits Circuit = complete path of electron flow Parts of a Circuit: Energy source Conductor Load * Switch Electrons flow from negative to positive WB – draw and example of an electrical circuit Circuit - The word circuit comes from the Latin word meaning to go around Conductor Load – converts energy to another form of energy - converts the electrical energy into heat Energy source Many also include a switch A device that turns the circuit on or off by closing the curciut blocking electron flow The circuit is turn off when the switch is open Part I: Act Out an Electric Circuit 2. Tell students that they cannot see electricity because electrons, the charged particles whose movement through a substance creates electricity, are too small to be seen even with a microscope. When electrons flow through certain substances (like copper wire), they form an electrical current. Electrical current provides energy to power all kinds of things, from video games to refrigerators to cars! 3. Act out an electric circuit, as follows: Ask students to join you in forming a circle. Tell students that you represent a battery and they represent a wire conductor. The circle represents a circuit. (Note: The word circuit comes from the Latin circuitus, which means "to go around.") Distribute an object -- like a ball, a book, or an eraser -- to each member of the circle, including yourself. Ideally, everyone should have the same object. Tell students that these objects represent electrons inside a wire conductor. Explain that a wire conductor is full of electrons. Remind students that you are playing the part of the battery in this circuit, and explain that all batteries have a positive end, represented by your left hand, and a negative end, represented by your right hand. Pass your "electron" to the student on your right. The student receiving your electron should in turn pass the one he or she is holding to the right. Have students continue passing on electrons to the person to their right. Tell students that because electrons share the same negative charge, they repel one another, which keeps them moving along in the same direction. State again that the flow of electrons through a conductor is called electrical current. 4. Tell students that as long as the circle remains intact and the electrons continue to flow, their circuit is closed. To illustrate what happens when a circuit breaks, or opens, create a gap in the circle of students that is too wide across to pass electrons. The current will stop as a result. Examples Water in a hose – if the hose is connected to a tap already has water in it and you turn on the tap, water comes out the other end When and energy source is connected to a circuit, electrons in a circuit push or repel the other elesctrons nearby As soon as one elcetron starts to move it pushes the next one which pushes the next one and so on Marbles in a tube

Functions of the Parts of a Circuit Energy source – provides energy for the electrons in the circuit Conductor – wires that carry the current (electrons) around the circuit Load – converts the electrical energy carried by the electrons to a useful form (light, heat, movement) * Switch – controls when the electricity can flow (not a necessary part of the circuit

Electrochemical Cells Electrochemical Cell = a pack of chemicals that converts chemical energy into electrical energy that is stored in charged particles A battery is a combination of electrochemical cells Battery – combination of electrocemical cells

Electrochemical cells include: 1 Electrolyte Liquid or paste that conducts electricity Contains chemicals that form ions Ex. Citric acid 2 Electrodes Metal strips that react with the electrolyte Ex. Zinc and Copper Reaction  electrons collect on one of the electrodes (- charge), and electrons are lost from the other electrode (+ charge) WB – What is an ion Ion – groups of atoms that has become electrically charges by loosing or gaining electrons \ Rxn between electrode and electrolyte

Types of Electrochemical Cells Wet Dry Fuel

Wet Cells = an electrochemical cell that has a liquid electrolyte Example: Car battery

Dry Cells = an electrochemical cell that has a paste electrolyte Example: Simple batteries Eventually the chemicals in a dry cell wil be used up and can no longer separate charges When you are finished using a dry cell it is important to recycle them and not throw them out Because : They contain toxic materials (heavy metals) Resposible for 50% of all heavy metal found in land fills Some are recharable Chemical energy in the cell can be revered using external energy source to run electricity back into the cell Restores reactants Less impact on the environment because they can be resused Terminal – ends of a dry cell or battery, where we can make connections WB – what type of batteies are better for the environment and why? Rechargeable or non-recharable

Fuel Cells = an electrochemical cell that generates electricity directly from a chemical reaction with fuel Example: Electric Car Battery Hydrogen fuel cells Not used up like other cells As electricity is produced more fuel is added Most of the energy produced is wasted as heat

Why Do Batteries Die? When the chemicals in a battery are used up the battery dies. Batteries should always be recycled because they contain many harmful chemicals such as mercury, lead and cadmium. Rechargeable Batteries have chemical reactions that can be reversed with an input of energy.

Homework Questions 1-5 pg. 436 Handouts The Wet Cell