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Unit 8: Electricity and Magnetism Notes Chapter 4: Electricity and Magnetism Lesson 1: What is Static Electricity Two Kinds of Change An electric charge is a basic property of the tiny particles that make up matter Electric charge can be either positive or negative Positive and negative charges cancel out each other Neutral is when you have a balance of positive and negative charges Negatively charged- has more particles with a negative charge Positively charged- has more particles with a positive charge Opposite charges attract- pull toward each other Same charges repel- push away from each other Static electricity is the buildup of charges in one place o Ex. When clothes crackle and stick together after taking them out of the dryer Separating Charges Negative charges can be moved by rubbing an object against another (positive charges CANNOT be moved) Two ways to separate charges: o rubbing objects together o bringing a charged object near a neutral object Electric Forces An electric force is the push or pull between objects that have different charges Positive and Negative electric charges have electric fields, the space in which an electric force acts, around them As you move farther from a charged object, the force gets weaker The field of a positive charge attracts a nearby negative charge or repels a positive charge (refer to the diagram on pg. 182-183) Lesson 2: What Makes a Circuit Moving Charges In static electricity, an object becomes charged when it gains or loses negative charges The charge jumps only if it has a path- like from the carpet to you, or from you to the doorknob In electric current, the charges have a path to follow, they flow, or move (a steady flow of charges) An electric circuit is a closed path that electric current follows. (the battery and the light bulb) Series Circuits A series circuit has only one path for its current to follow In a series circuit the current flows from the battery (power source), through the wires, passes through each device (light bulb), and flows back to the battery (closed circuit) The same amount of current flows to each device Removing any device causes all devices to stop working (open circuit) Parallel Circuits A parallel circuit has more than one path for current to flow It’s more convenient to use than the series circuit because even if the charge is blocked on one path it still has another path to follow In parallel circuits, the current is split between the paths Parallel circuits allow people to use devices separately. (light switches in our homes) Resistance The amount of current that can flow through a circuit depends on its resistance Resistance is how much a material opposes the flow of current The greater the resistance, the less current can pass through a circuit Examples of high resistance would be a light bulb- as the current passes through the filament, it resists the flow causing it to get hot- then glow from the heat High resistance is used to produce heat and light Examples-toasters, space heaters, light bulbs In a short circuit, current flows where it isn’t wanted- they prevent the rest of the circuit from working properly Lesson 3: Conductors and Insulators Conductors A conductor is a type of material through which negative charges can move easily. Metals are good conductors because they allow negative charges to move through them easily Negative charges are “pushed” through a conductor Examples of conductors are copper and silver Insulators An insulator is a material that resists the flow of electricity Examples of insulators are cardboard, foam, rubber, or plastic Lesson 4: What Makes an Electromagnet Making a Magnetic Field A magnet that has coils of current-carrying wire around an iron core is called an electromagnet. An electromagnet is a temporary magnet It only has a magnetic force only when an electric current passes through the wire When there is not current, the electromagnet doesn’t work Controlling Electromagnets Electromagnets can be controlled by turning them on and off They can also be controlled by switching the connections to the battery- which switches the magnetic field (the N field becomes the S field) They can be made stronger by: o Using more coils o Increase the strength of the electric current (add more batteries) Need to Know Unit 8: Electricity and Magnetism All definitions Characteristics of conductors (allow electricity to flow) and insulators (do not allow electricity to flow) Examples of conductors (metals, salt water etc…) and insulators (plastic, wood, etc…) Be able to draw and label a circuit Be able to describe how a circuit works Know the difference between a series and a parallel circuit Know what an electromagnet is and how it works Be able to draw and describe an electromagnet Why objects attract (opposite charges) and repel (alike charges)