1. Ohm’s Law, Power and Energy ENTC 210: Circuit Analysis I Rohit Singhal Lecturer Texas A&M University

2. Administrative Tasks Lab details  TA – Mr. Pankaj Bhagawat  Sections Merge  Starts today!

3. Review - Atoms and their structure

4. Review - Coulomb’s Law Like charges repel, opposites attract  F = k Q 1 Q 2 / r 2  K = 9 x 10 9 N m 2 /C 2

5. Review - Current Rate of flow of charge 1 Amp = 1 Coulomb / 1 Second.

6. Review - Equations I = Q/t Q = I x t t = Q/I

7. Review - Voltage Voltage is always measured between two points. It is defined as the difference of potential between the two points. Measured in volts 1 volt is defined as the potential difference, which results in an energy exchange of 1 Joule due to the movement of 1 Coulomb across it.

8. Review - Conductivity Copper is the most popular conductor. MetalConductivity (%) Silver105 Copper100 Gold70.5 Aluminum61 Tungsten31.2 Nickel22.1 Iron14 Constantan3.52 Nichrome1.73 Calorite1.44

9. Review - Resistance R = ρ L/A ρ is the resistivity of the material (units?)

10. Material ρ (10 -8 Ohm-Metres) Silver1.645 Copper1.723 Gold2.443 Aluminum2.825 Tungsten5.485 Nickel7.811 Iron12.299 Tantalum15.54 Nichrome99.72 Tin Oxide250 Carbon3500

11. Review - American Wire Gage (AWG) sizes AWG #Diameter (in)Ω /1000ft. 00000.460.0490 0000.4090.0618 00.3250.0983 10.2890.1240 20.2570.1563 40.2040.2485 100.1020.9989 140.06402.525 280.012664.90

12. Review - Color Coding 5 Bands of code (3 are mandatory) Bands 1 - 3  the value of the resistor Band 4  the range (tolerance) Band 5  the reliability

13. Review - Color Code (Band 1-3) ColorValue Black0 Brown1 Red2 Orange3 Yellow4 Green5 Blue6 Violet7 Gray8 White9

14. Review - Band 3 (special cases) Gold = 0.1  Red Blue Gold = 2.6 Ohm Silver = 0.01  Red Blue Silver = 0.26 Ohm

15. Review - More Bands Band 4Tolerance Gold5% Silver10% None20% Band 5Reliability (after 1000 Hrs of use) Brown1% Red0.1% Orange0.01% Yellow0.001%

16. Ohm’s Law! Current flows because Electrons flow from one point to another. What causes the flow of electrons?

17. Ohm’s Law! Current flows because Electrons flow from one point to another. What causes the flow of electrons?  Voltage (potential difference)

18. Ohm’s Law! Current flows because Electrons flow from one point to another. What causes the flow of electrons?  Voltage (potential difference) More voltage results in more or less electrons?

19. Ohm’s Law! Current flows because Electrons flow from one point to another. What causes the flow of electrons?  Voltage (potential difference) More voltage results in more or less electrons?  More electrons

20. Ohm’s Law! So does that mean that Current is proportional to Voltage?

21. Ohm’s Law! So does that mean that Current is proportional to Voltage?  Yes The more the voltage the more is the current

22. Ohm’s Law What is the effect of resistance?

23. Ohm’s Law What is the effect of resistance? Do more electrons flow when there is a high resistance?

24. Ohm’s Law What is the effect of resistance? Do more electrons flow when there is a high resistance?  No

25. Ohm’s Law What is the effect of resistance? Do more electrons flow when there is a high resistance?  No The higher the resistance, the less is the current.

26. Ohm’s Law What is the effect of resistance? Do more electrons flow when there is a high resistance?  No The higher the resistance, the less is the current. Current is inversely proportional to the resistance.

27. Ohm’s Law I = V/R V=IR R=V/I

28. Question

29. Power Power dissipated by charge flowing through a resistor  P = VI  P = V 2 /R  P = I 2 R

30. Question

31. Energy Energy = Power x Time

32. Question