1. Electricity

2. Electricity is a flow of electrons (negative charge) through wires and components. The rate at which electrons flow is called current. Current is measured in Amperes (Amps). You can measure the current in a circuit with an ammeter. Current

3. Current Equation Electric current = amount of charge amount of time ItemSymbolUnit Unit Abbreviation CurrentI Ampere (Amps) A ChargeQCoulombC TimetSecondss

4. Conceptual Question

5. 6C/3s = 2 Amperes (Amps) 3C/1s = 3 Amperes (Amps) Distance NOT Charge!

6. Current Sample Problem If a rabid squirrel with 3 x 10 -5 C holds a neutral acorn for 15 seconds, what is the current traveling from the squirrel to the acorn?

7. 1.What is the current if 3600 C of charge passes a point in 17 min? * What do you have to change? (HINT – Time)

8. 1.What is the current if 3600 C of charge passes a point in 17 min? * What do you have to change? (HINT – Time)

9. 2.For what period of time must a current of 0.22 A, flow if 7.5 x 10 18 electrons are passed through it? *What do you have to change? (HINT – Total Charge)

10. 2.For what period of time must a current of 0.22 A, flow if 7.5 x 10 18 electrons are passed through it? *What do you have to change? (HINT – Total Charge)

11. 3.What is the charge of a current that has 25 A and takes 5 seconds to round the circuit?

12. A simple loop for the current to flow round Components are connected end-to-end, one after the other. If one bulb ‘blows’ it breaks the whole circuit and all the bulbs go out. Series Circuit

13. Junctions Parallel Circuits Multiple loops for the current to flow round Components are connected & at some point the current splits & then comes back together. These locations are called Junctions. If one bulb ‘blows’ there is still a complete circuit so the other bulb stays alight.

14. Direct Current (DC) DC = Direct Current – Supported by Thomas Edison – current flows in one direction Example: Battery DRAW THESE!

15. Edison

16. Alternating Current (AC) AC = Alternating Current- – Supported by Nikola Tesla – current reverses direction many times per second. This suggests that AC devices turn OFF and ON. Example: Wall outlet DRAW THESE!

17. Tesla

18. What do you think? Between Edison & Tesla, who do you think contributed the most to society & why? Why do we know more about Edison than Tesla?

19. Voltage (V) Voltage is the difference between two charges. – also called Potential Difference & Electric Potential. Batteries have a + charge on one side and a - charge on the other. – The difference between those 2 charges is the voltage of the battery.

20. -Voltage use a voltmeter to measure the voltage of a battery or the voltage drop of a device. -Voltage drop is how much voltage is lost from one side of a device to the other side of the device. Voltage

21. Resistance (R) Resistance (R) is the restriction of electron flow. -As current travels through a device it slows down because the electrons are attracted to the protons in the device. -Resistance is a measure of the change in current. -The unit for resistance is the Ohm, 

22. “The voltage (potential difference) is directly related to the current, when the resistance is constant” ItemSymbolUnit Abbreviation VoltageVVoltsV CurrentIAmperesA ResistanceROhm’s 

23. Voltage Sample Problem 1.What is the voltage of a circuit with 15 amps of current and a light with 7 ohms of resistance ?

24. Voltage Practice Problems (V=IR) 1.What is the voltage of a circuit that has a current of 75 A with a resistance of 10  2.What is the resistance of a circuit that has a current of 150 A with a voltage of 35 V  3.What is the current of a circuit that has a resistance of 50  and a voltage of 30 V?

25. Voltage Practice Problems (V=IR) 1.V = IR = 75 A x 10  = 750V 2.V = IR R = V/I = 35 V / 150 A .23  3.V = IR I = V/R = (30 V)/(50   0.6 A

26. Power (P) POWER is the rate at which work (energy) is done. Joules/Second or Watts. Electricity in Kilowatt hours (kW/h). ItemSymbolUnit Abbreviation PowerPWattsW CurrentIAmperesA VoltageVVoltsV

27. Power Sample Problem Calculate the power rating of a home appliance (in kilowatts) that uses 8 amps of current when plugged into a 120-volt outlet.

28. Power Practice Problems (P=IV) 1.What is the power of a circuit that has a current of 80 A with a voltage of 20 W  2.What is the current of a circuit that has a a voltage of 35 V  & it’s power is 770 W? 3.What is the voltage of a circuit that has a current of 50 A  and 650 W of power?

29. Power Practice Problems (P=IV) 1.P=IV P = (80 A)(20 V)  P = 1600 W 2.P = IV I = P/V I = 770 W / 35 V I = 22 A 3.P = IV V = P/I V = 650 W / 50 A V = 13 V

30. Energy(E = Pt) Energy is the amount of Power produced in a certain time – (Watts)(seconds) or Joules ItemSymbolUnit Abbreviation EnergyEJoulesJ PowerPWattsW timeTSecondss

31. Energy Sample Problem How much power does a light bulb use if it uses 150 watts of energy over 30 seconds?

32. Energy Practice Problem 1.Calculate the Energy of a 75 watt light bulb that burns for 15 seconds. 2.Find the Power of a circuit that has 1.5 x 10 3 Joules of energy that runs for 50 sec. 3.What is the time that is needed to produce 1000 J with the power of 250 W?

33. Energy Practice Problem 1.E = Pt = (75 W)(15 sec) E = 1125 J 2.E = Pt P = E/t = 1.5 x 10 3 J / 50 s P = 30 W 2.E = Pt t = E/P t = 1000 J/250 W? t = 4 s