EEGR2111 L2

Current - again Current - direction Passive convention: current into positive voltage terminal Passive convention: POWER ABSORBED by element Above: if v=1, i=2 then p=2 W absorbed by element If i=-2 then p=-2 W and power is SUPPLIED by element In a total circuit absorbed=supplied
Example L2-1: Let v=2 and i=3 Find the energy absorbed between time 0 and 5 seconds What are units? What if i=-4? What if time -5 to -1?
Example L2-2: A 12 V battery is connected to an element and the current measuerd leaving the + terminal is 1 mA. What is the power absorbed by the element? What is the power absorbed by the battery? Is this possible? What is the energy delivered to the element in 1 hour?
Example L2-3: A 1.2 V NiCd battery stores approximately 5000 Joules of energy. What wattage is a light-bulb that draws 400 mA from the battery? How long will the battery last?
Example L2-4: Suppose: What is the power p(t)? What is the total energy absorbed for all time?
Linear Elements Suppose v=f(i) (or i=f(v)) 1. Superposition: if v1 = f(i1) and v2 = f(i2) then v1 + v2 = f(i1 + i2) 2. Homogeneity: if v3 = f(i3) then k v3 = f(i3) for any constant k Linear: if 1 and 2 above are true. The function f() is linear (element model) Alternatively k1 v1 + k2 v2 = f( k1 i1 + k2 i2)
Example L2-5: Is v = i R linear?
Example L2-6: Is v = i R + 2 linear?
Example L2-7: is i=dv/dt linear?
Example L2-8: Is the above function (plotted) linear? Why?