Electricity 2 Voltage, Potential Difference and Electromotive Force
Aims of the Lesson- Voltage <ul><li>Recall the meanings of the phrases ‘ potential difference ’ and ‘ electromotive force ’ </li></ul><ul><li>Recall that in a series circuit the sum of the voltages is equal to the voltage across the whole circuit. </li></ul>
Voltage <ul><li>Page 118 </li></ul><ul><li>- Worksheet on Alexandro Volta (basic notes on voltage) </li></ul><ul><li>Complete questions 9 and 10 pg 121 </li></ul>
Total PD in a circuit <ul><li>Read page 119 and 120 </li></ul><ul><li>Copy out the statement in the blue box. </li></ul><ul><li>Complete the Worksheet ‘Understanding Voltage’ </li></ul>
Energy Saver Light Bulb <ul><li>Transfers Electrical to Light and Heat </li></ul><ul><li>220 Joules of energy transferred for every coulomb of charge passing through </li></ul><ul><li>For a current of 140 mA (0.14 A) </li></ul><ul><li>0.14 Coulombs passing through each second </li></ul><ul><li>Energy = 220 / 0.14 = 1571 J </li></ul>140 mA 220 V
Aim of the Lesson <ul><li>Clearly define what is meant by the current and voltage of a circuit! </li></ul><ul><li>Recall why a voltmeter is placed into a circuit in parallel and an ammeter is placed into a circuit in series </li></ul>
Eh… explain that to me please! <ul><li>What does the current flowing a circuit mean? </li></ul><ul><li>What does the voltage of a component mean? </li></ul>Number of Coulombs Going past a point every second Amount of Energy transferred For every Coulomb That passes through a component
Voltmeter action <ul><li>How does a voltmeter go into a circuit? </li></ul>First of all we need a circuit… Equipment you need- What is the Voltmeter measuring? Energy in and energy out , for each coulomb passing through a component
Sorry Sir but I’m gonna’ have to search you… What have you got on you, Mr Coulomb?
Experiment- Investigating Voltage How does the voltage of a component in a series circuit compare to the voltage of a component in a parallel circuit? The following two circuits are set up and the voltage is measured across both 1.5 V batteries and across each 1.5V bulb individually.
Experiment- Investigating Voltage V 1 = V 2 = V 3 = V 4 = V 5 = V 6 = Series Parallel + V 1 Series + Parallel
Investigating Voltage - Conclusion <ul><li>In a series circuit the voltage supplied by the battery is divided between the components. </li></ul><ul><li>In a parallel circuit the voltage supplied is the same as the component’s voltage. </li></ul><ul><li>The energy each coulomb received (from the battery) is equal to the total energy given out as it goes round the circuit (conservation of energy). </li></ul>
Voltage in a series circuit V V V 2V If the voltage across the battery is 6V… … and these bulbs are all identical… … what will the voltage across each bulb be?
Voltage in a series circuit 4V V V If the voltage across the battery is 6V… … what will the voltage across two bulbs be?
Voltage in a parallel circuit 4V 4V If the voltage across the batteries is 4V… What is the voltage here? And here? V V
Summary In a PARALLEL circuit : Current SPLITS UP down each “strand” Voltage is THE SAME across each”strand” In a SERIES circuit: Current is THE SAME at any point Voltage SPLITS UP over each component
An example question: V 1 V 2 6 V 3 A A 1 A 2 V 3 A 3 What is the easiest path for the Coulombs of Charge? All bulbs are identical in power rating
Advantages of parallel circuits… <ul><li>There are two main reasons why parallel circuits are used more commonly than series circuits: </li></ul><ul><li>Extra appliances (like bulbs) can be added without affecting the output of the others </li></ul><ul><li>If one appliance breaks it won’t affect the others either </li></ul>
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