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Task : Copy and fill in the blanks Electrons are ………….. charged sub-atomic particles. They move around the circuit through ……………. materials such as metal wires. A cell has a positive and negative side. The ……….. flow out of the negative side and ……….. the positive side. This is called the electron flow. electrons negatively towards conductive

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Modelling Electricity To be able to use a model to explain current and voltage in electrical circuits

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Symbols Look at the following symbols for components – can you name them all? CellResistorBulbSwitch BatteryBuzzerFuseVoltmeter AmmeterMotorVariable Resistor

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Key Terms What is current, voltage and resistance? Current – the flow of electrons around the circuit Voltage – driving force which pushes the current around Resistance – anything in the circuit which slows the flow down

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Task 2: Voltage and current = the electrical energy Voltage is a measure of the energy carried voltage Current Voltage is used up in components Voltage is measured in volts, V Voltage is measured with a voltmeter Current is the rate of flow Current is not used up, what flows into a component must flow out. Current is measured in amps (amperes), A Current is measured with an ammeter

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Series Circuits What are series circuits? Series circuits are ‘all or nothing’ – the different components are connected in a line, end to end Disconnecting one component breaks the circuit, meaning all the components stop +- A The same current flows through all parts of the circuit The size of the current depends on the voltage and resistance (I = V/R) The total voltage is shared between the components - the bigger the resistance of a component the bigger its share of the voltage

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Series Circuits + - A 6V 2V 2.5V1.5V 0.5A Voltages add to equal the supply: 1.5V + 2V + 2.5V = 6V Total resistance is the resistance of all the components: 3 Ω + 4 Ω + 5 Ω = 12 Ω Current = voltage ÷ resistance: 6 ÷ 12 = 0.5A 5Ω5Ω 3Ω3Ω 4Ω4Ω

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Parallel Circuits What are parallel circuits? In parallel circuits each component is separately connected to the +ve and –ve of the supply Removing one component barely affects the others All components get the full voltage The current through each component depends on its resistance – the lower the resistance the more current that flows through The total current flowing around the circuit is equal to the total of all the currents in the separate branches branch 1 branch 2

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Parallel Circuits + - 6V 5.5A Voltages are all equal to the supply: 6V Total resistance is less than the smallest resistance: < 2 Ω Current (A 1 ) equals the sum of all the branches: A 2 + A 3 + A 4 etc… (5.5A) 4Ω4Ω A1A1 A2A2 A3A3 A4A4 6V 1.5A 3A 1A 2Ω2Ω 6Ω6Ω

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Assessment Complete the circuits worksheet

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Assessment 1. E, F, T, J, or L 2. A, B, C, D, G, H, or K 3. A and I 4. Add some more cells (>2 cells = a battery) 5. B 6. B, D, G, H, or K (2 of these) 7. A or C 8. The switch is open 9. B, D or K 10. F

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Assessment 11. V V 12. B, D or K

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Assessment 13. 14. 6A – the current should split evenly down each branch if the resistance of the components in each branch is equal 15. 2.5V – the voltage is shared between all the components in a series circuit

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