Topic 2

1. Topic 2 Power & Energy (Section 1.6)

2. + v 1 - 2 Solution By definition so Sample Problem 1.3 the current entering the element is given by i Calculate the total charge in microCoulombs entering the device at terminal 1 Since this is in coulombs the answer is 4000 µC Power and Energy

3. Power p = power in watts w = energy in joules t = time in seconds By the chain rule Which means that Power and Energy

4. i + + v 1 1 1 1 - v 2 2 2 2 Power absorbed by ckt Power delivered by ckt i - - v v + + Power delivered by ckt Power absorbed by ckt i - i Power and Energy

5. Single cell produces about 1.5 volts 1.5 V It stores charge internally, usually chemically Batteries Think of it as being 1.5 volts “high” We can make bigger cells, that store more charge, (or little ones that store less) But we can’t make the cells any higher Although different cell technologies have somewhat different heights Power and Energy

6. Cell Technologies Power and Energy 1. Fully charged

7. 12v 6 v To make a battery we stack cells up Making a higher and higher voltage “hill” Three lead-acid cells makes a 6 volt battery And 6 gives us a car battery Power and Energy

8. Water tower stores energy Battery stores energy Electricity vs Gravity Water tower holds mass (volume) Water tower has a height Battery holds charge (capacity) Battery has a “height” (voltage) Power and Energy

9. 1 i 1 2 + battery v heater 2 - From the battery’s point of view From the heater’s point of view Hooking a Battery to a Heater The battery voltage appears across the heater Current flows from the battery into the heater It produces power It absorbs power Power and Energy

10. Given + v 1 i - 2 By definition & So So & Sample Problem 1.6 Given Calculate the total energy in joules delivered to the element Solution Voltage was in Kv Integrating… Power and Energy

11. Problem 1.27 -36000 Power and Energy