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Transcript
GPS • S8P5. Students will recognize characteristics of gravity, electricity, and magnetism as major kinds of forces acting in nature. Demonstrate the advantages and disadvantages of series and parallel circuits and how they transfer energy. EQs How are electric circuits wired? What exactly is electricity? What are the advantages and disadvantages of series and parallel circuits? How do they transfer energy? Electricity is the movement of electrons • Atoms contain charged particles known as protons (+) and electrons (-) • Like charges repel • Unlike charges attract Electrons move from an area that is negatively charged (extra electrons) to an area that is positively charged (wanting electrons). Unlike charges attract Like charges repel. Electricity Electricity occurs in 2 different forms 1. Static 2. Current Is stationary Flows around circuit E.g. Brush your hair E.g. turn on light Wool socks in tumble dryer Walkman Static Electricity Occurs with materials which are insulators Rubbing adds or removes electrons Object becomes charged Like objects repel, unlike attract Current Electricity Electrons flow through a conductor Negative to positive Circuit = continuous loop for electrons to flow Needs energy supply Energy user Series circuit • • • • • Has a single loop for electrons to travel round Components are connected one after another Current has to travel through all components Current is the same at all points Voltage is shared between components Uses for Series Circuits Series circuits are useful in wiring burglar alarms. If any part of the circuit fails, there will be no current in the system and the alarm will sound Parallel circuit • • • • Has two or more paths for electrons to flow down Current is shared between the branches Sum of the current in each branch = total current Voltage loss is the same across all components Uses for Parallel Circuits Almost all appliances are built with parallel circuits so that they will keep working if part of the system fails. Electricity • Electricity is forced around a circuit by an electrical force field • Flow of electricity around a circuit is called CURRENT (I) • Current measured in amps (A) • Voltage (V) – Increase or decrease in the amount of electrical energy carried by the current. Current (I) • Current is the flow of electrons around a circuit • Measured in amperes (amps) • DC = direct current like battery • Electrons flow in one direction • AC = Alternating current like mains • Electron flow changes direction 50x per second Ammeter • Measures CURRENT (I) • Unit = Amp (A) • Current is flow of electrons • Connect in series at the point you wish to measure • RED to RED and BLACK to BLACK Voltage (V) • Gain or loss of energy as it passes through a component • Voltage lost = voltage gained • In series voltage loss is shared between components • In parallel voltage loss is the same across all components Voltmeter • Measures voltage • Unit = Volt (V) • Voltage increases as it passes through energy suppliers • Voltage is decreased as it passes through users • Connect in parallel around a component SUMMARY In Series Current Voltage Always the same Voltage from source = voltage used Voltage is shared between power users In Parallel The branches share electrons and add to the total Voltage is the same in all branches resistance R The amount that a component slows the current or the opposition to the flow of electric charge. Resistance is measured in ohms. grounding The creation of a harmless, lowresistance path—a ground—for electricity to follow. Grounding is an important electrical safety procedure. Static Electricity Electric Discharge The loss of static electricity as charges move off an object is called electric discharge. One of the most dramatic examples of electric discharge is lightning. The next slide shows how lightning is formed. AC and DC There are two kinds of electric current—direct current (DC) and alternating current (AC). Parts of an Electric Circuit Forming a Loop An electric circuit is a complete, closed path through which electric charges flow. All circuits need three basic parts: an energy source, wires, and a load. A Switch to Control a Circuit Sometimes, a circuit also contains a switch. A switch is used to open and close a circuit. Circuit Failure Broken wires or water can cause a short circuit. In a short circuit, charges do not go through one or more loads in the circuit. Fuses A fuse has a thin strip of metal. Fuses keep charges from flowing if the current is too high. Circuit Breakers A circuit breaker is a switch that automatically opens if the current is too high. Charges stop flowing. Electrical Safety Tips Do not overload circuits by plugging in too many electrical devices. Do not use electrical devices near water.