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# Y8 Electricity 03 measuring current

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### Y8 Electricity 03 measuring current

1. 1. Measuring Current <ul><li>Learning Objectives : </li></ul><ul><li>Describe current as a flow of electrons. </li></ul><ul><li>Link amount of cells in a circuit to the size of the current. </li></ul>
2. 2. Measuring electric current We can measure the amount of electric current flowing through a circuit using a device called an “ammeter”. Current is measured in Amperes . A
3. 3. What is the trend here? 2 electrons per second = 1A 8 electrons per second = 4A 4 electrons per second = 2A 12 electrons per second = 6A
4. 4. Rich questions: <ul><li>Which way do electrons flow? </li></ul><ul><li>Do electrons always flow the same way around a circuit? </li></ul>
5. 5. Measuring Current <ul><li>How much the current is flowing is the number of electrons passing a point every second. </li></ul><ul><li>Therefore current depends on how many electrons are moving and how fast they are moving. </li></ul><ul><li>Current & Voltage in a circuit </li></ul>
6. 6. The unit of measure for current is the amp , which has the symbol A. A Measuring current Current is measured using a device called an ammeter . In a circuit diagram, an ammeter is shown by the symbol . When measuring the current through a component, the ammeter is always connected in series (in the same loop) with that component. A A
7. 7. Experiment 1: Current in series circuit 1 2 <ul><li>Set up the circuit as shown above. </li></ul>Circuit 1 <ul><li>Measure the current using the ammeter at positions 1 and 2. </li></ul>R1 A A
8. 8. Experiment 1: Current in a series circuit 3 <ul><li>Add another lamp into the circuit (R2) and another ammeter after it. </li></ul>A R2 Circuit 2 1 2 <ul><li>Now measure the current using the ammeter at positions 1, 2 and 3. </li></ul>R1 A A
9. 9. Experiment 1: Current in a series circuit – results Circuit 2 results: Current at position 1 = Current at position 2 = Current at position 3 = Circuit 1 results: Current at position 1 = Current at position 2 = Circuit 1 Circuit 2 1 2 1 2 3 Draw each circuit and trace the path of the electrons through the circuit R 1 A A R1 R2 A A A
10. 10. Experiment 1: Current in a series circuit – summary Circuit 1 The current at different positions in the circuit, before and after the lamps, was the _______. Current is _____ used up by the components in the circuit. Circuit 2 Increasing the number of components in the circuit ________ the current. The current at all points in a series circuit is the _______. same / same / decreased / not Circuit 1 Circuit 2 R 1 A A R1 R2 A A A
11. 11. Current in a series circuit In other words, the current in a series circuit is THE SAME at any point If the current here is 2 amps… The current here will be… The current here will be… And the current here will be…
12. 12. Compare and contrast <ul><li>Do not attempt to answer the question initially </li></ul><ul><li>Discuss with neighbour which of two questions do you think is highest level and why? </li></ul><ul><li>Level </li></ul><ul><li>Current is a flow of electrons </li></ul><ul><li>Would there be more or less electrons flowing if the current was large? </li></ul><ul><li>Level </li></ul><ul><li>Current is a flow of electrons </li></ul><ul><li>Which of the three currents (2A, 5A or 10A) would have the largest flow of electrons? </li></ul>
13. 13. Next lesson <ul><li>What do you think we should be learning next lesson? </li></ul>
14. 14. Measuring Current <ul><li>Learning Objectives : </li></ul><ul><li>Describe current as a flow of electrons. </li></ul><ul><li>Link amount of cells in a circuit to the size of the current. </li></ul>