how to compute differential algebraic equations on RL circuit?

[David Goodmanson]

Hi Lahari,

It appears that the current source here is arbitrary and is an input to the problem. So you need to specify the current and find its derivative either algebraically or numericallly. This is done independently of what the circuit itself happens to be.

[LAHARI NAGELLA]

I need matlab code for that problem and also how to plot a graph.

Answer 1

[Ameer Hamza]

Try this

syms G e1 e2 I(t) iL L 
DI = diff(I, t);

eq1 = G*(e1-e2) == I;
eq2 = -G*(e1-e2)+iL == 0;
eq3 = L*DI-e2 == 0;

sol = solve([eq1, eq2, eq3], [iL e1 e2]);

Result:

>> sol.iL
ans =
I(t)
>> sol.e1
ans =
(G*L*diff(I(t), t) + I(t))/G
>> sol.e2
ans =
L*diff(I(t), t)