How to use equation??

Question

hi

i need to calculate the steady states currents and magnitudes of steady state voltages accross a resistor and inductor using the equation i(t)=(v/r) (1-e^-Rt/L)

i know v=6 r=10 L=0.10

i am not sure how to use my calculator for the log bit

please help!!!

Answer 1

This is a problem in transient condition. However the answer sought is under steady state condition, i.e., the transients have subsided  sufficiently the steady state voltage across the resistor is 6/10 = 600 mA assuming the inductor is ideal with zero resistance and the voltage across the inductor is zero.

The current raises from zero to 600 mA

                                 with time constant =  L/r

Answer 2

In the steady state, time is infinite, so the exponential term goes to zero (the inductor influences things only while the current through it is changing).  So, E = I R works just fine -- but the R will be the sum of the resistances of the inductor and the resistor, assuming that these are connected in series.