# step response of a circuit having an inductor loop

What is the step response of $I_1(t)$ in the following circuit? (I mean if we apply step as input I what will be the I1?

I simply used Laplace transform and calculated the step response, but it was wrong according to the book I'm reading. It says in this circuit the current is not continuous at t=0 because we have a inductor loop, which I don't understand.

simulate this circuit – Schematic created using CircuitLab

• Thanks for the accept, but feel free to hold off before giving it out. You might get an actual answer about Laplace transforms if you give people around the world 24 hours to read the question. (As for myself, in 15 years of work and 5 years of grad school, I've never used Laplace transforms to solve a real problem, so I don't bother giving answers in those terms) Jan 21 '15 at 19:24
• This answer completely addressed my problem, because now I can solve all such problems with discontinuities by adding series or shunt resistances. Anyway, I'll wait till tomorrow. Thanks again! Jan 21 '15 at 19:30

This circuit is not adequately modeled with ideal components. In this model, for the current source to produce a step output, its voltage must approach infinity, because it will be trying to produce an infinite $\frac{\mathrm{d}I}{\mathrm{d}t}$ through an inductive load.
• You can do that, but the result will be $v(0^+)\to\infty$. So it still won't tell you what a real circuit would do. Jan 21 '15 at 19:13