When I enter the following command I get imaginary solutions:
R = 5; **L = 0.05**; EMF = 5 Cos[120 t];
cur1 = DSolve[{R i [t] + L i'[t] == EMF, i[0] == 1}, i, t][[1, 1, 2]][ t]
Solution: (0.409836 - 4.3368110^-17 I) E^(-100. t) ((1.44 + 2.5819610^-16 I) + (1. + 0. I) E^(100. t) Cos[120. t] + (1.2 + 1.26982*10^-16 I) E^(100. t) Sin[120. t])
But if I enter the following i get real solutions:
R = 5; **L = 1/20**; EMF = 5 Cos[120 t];
cur1 = DSolve[{R i [t] + L i'[t] == EMF, i[0] == 1}, i, t][[1, 1, 2]][ t]
Solution:
1/61 E^(-100 t) (36 + 25 E^(100 t) Cos[120 t] + 30 E^(100 t) Sin[120 t])
Any help understanding this would be appreciated. I am currently using Mathematica v11.1. But I have the same issue on Wolfram Cloud.