3. calculate power in a basic electrical circuit

3. Calculate power in a basic electrical circuit

1. 202/2 – Know the principles of basic electrical circuits Outcome 2.3 – Calculate power in a basic electrical circuit Unit 202 Principles of electrical science

2. 2.2 Apply Ohm’s law to electrical circuits Series, parallel. Last session

3. 2.3 Calculate power in a basic electrical circuits Series, parallel. This session

4. Power measured in watts A watt is an amount of work done in a certain time. One watt is equal to one J oule per second.

5. Power measured in watts When current flows through a resistor there is a voltage drop. Due to friction between electrons, electrical energy is converted into heat or light or both. Write down three examples of this?

6. Power measured in watts Kettle toaster Wall heater GLS Light bulb (tungsten or halogen) Soldering iron Hair straighteners Electric patio heater Immersion heater

7. Power measured in watts It is said that power is dissipated from a resistor. Or a resistor dissipates power.

8. Power measured in watts Two electrical factors affect power? __________ __________ Put these values in a formula.

9. Power measured in watts Power Voltage

10. Power measured in watts Power Voltage Lets look at V V= IxR So…. P I V V I R

11. Power measured in watts Power Voltage (I x I) = I² SO P=I²R P I I x R V I x R

12. Power measured in watts Power Voltage Lets look at I I= V R So…. P I V V I R

13. Power measured in watts Power Voltage (V x V) = V² SO P= V² R P V V R I V R

14. Choose the appropriate formula and calculate the power dissipated in each resistor? 230volts Calculate the total power dissipated in the series circuit? Calculate power 10 Ω 5 Ω 20 Ω

15. Calculate the total power dissipated 230volts Calculate the power dissipated in each resistor. Calculate power 5 Ω 7 Ω 13 Ω

16. Current and power Current decreases, power _________ Current increases, power _________

17. Voltage and power Voltage decreases, power _________ Voltage increases, power _________

18. Voltage and power In Barbados, supply voltage is 115V How long would a UK kettle take to boil?

19. Voltage and power Discuss in groups What would be the difference in a UK and Barbados kettle which both took the same time to boil?

20. Kettles UK Barbados 20 Ω 10 Ω 230v 115v Calculate power dissipated in both countries

21. How does resistance affect power dissipated?

22. How does resistance affect power dissipated? 20 Ω 10 Ω 230v 230v Calculate power dissipated in both circuits

23. Draw 5 resistors (1 to 100 Ω ) in a series/parallel configuration. Give it a supply voltage. Swap with a friend. Calculate the total power dissipated. Individual task

24. Consolidation Power triangles Formula transposed How does voltage affect power dissipated? How does resistance affect power dissipated?

25. 2.3 Calculate power in a basic electrical circuits Series, parallel. Consolidation

26. 2.4 State how instruments are connected into circuits in order to measure electrical quantities. Voltmeter, ammeter, wattmeter, ohmmeter. Next session