A length of metal wire has a radius of 0:002 m and a resistance of 0.1. When the potential difference across the wire is 14 V, the electron drift speed is found to be 0:000229 m/s. Based on these data, calculate the density of free electron in the wire. Answer in units of m^-3. r=.002m R=.1 Vd=.000229 V/R=i 14/.1=140 Vd= drift velocity. i/(Vd*A)=ne 140/(.000229*pi*.002squared)=4.86499826e10 j=neVd 11140846.02 (I tried plugging in this answer, it's wrong) 11140846.02/1e-3 = 1114084602e10 (I did this because it says answer is supposed to be in 1e-3) The answer is wrong I don't know why. A 72:5 W, 191.2 V light bulb is plugged into a 61:6 V outlet. If energy costs 4.7 cents/kWh, how much does it cost per month (30 days) to leave the light bulb turned on? Answer in units of cents. light bulb = 72.5W, 191.2V outlet = 61.6V Energy = 4.7 cents/kWh Days = 30 P/V = i 72.5/191.2 = .3791841 i*V=P .3791841*61.6 = 23.35574059W 23.35574059/1000 = .02335574059kW Pt = P*t .02335574059*30*24 = 16.81757322 Cost = P*cents 16.81757322* 4.7 = 79.04259414 cents This is also wrong, I don't know why. Any help is appreciated.