Hello , i was asked to find ''the Initial rate of growth of the current'' but am not quiet sure how do i do that ,

Full questions:
A coil having a resistance of 33ohms and an inductance of 3.3H is connected across a 100v dc supply.

So i used Ltspice to find it ,but am not sure what measurement i need to take .

Edit:i came up with (e/33)*(1-e^(-2/(3.3/33))) = 0.0823721764501894 , is that right ?

 

Ditch the simulator and recall your math. dI/dt at t=0 = ?
Maybe you've got it but I can't check your work if you don't show it.
This is homework, right?

 

Maybe the initial rate will is equal to L/V = 3.3H/100V = 0.033 s/A

 

Hello , i was asked to find ''the Initial rate of growth of the current'' but am not quiet sure how do i do that ,

Full questions:
A coil having a resistance of 33ohms and an inductance of 3.3H is connected across a 100v dc supply.

So i used Ltspice to find it ,but am not sure what measurement i need to take .

Edit:i came up with (e/33)*(1-e^(-2/(3.3/33))) = 0.0823721764501894 , is that right ?View attachment 235257

ive done 2 equations but not sure if 1st one or 2nd one is right or none of them at all , i did.
(e/33)*(1-e^(-2/(3.3/33))) = 0.0823721764501894
and
L/V=3.3H/100V=0.033 s/a

 

Ditch the simulator and recall your math. dI/dt at t=0 = ?
Maybe you've got it but I can't check your work if you don't show it.
This is homework, right?

so to find the initial rate you just do L/V ?

 

so to find the initial rate you just do L/V ?

\[ V\;=\;L\frac{di}{dt} \]
You have the fraction upside down

 

Vr = I • R ohm's law
Vi = L • dI/dt definition of an inductor
Vt - Vr - Vi = 0 Kirchoff's law

Vt - I•R = L•dI/dt algebra
dI/dt = (Vt - I•R)/L = V/L at t=0 when I=0

dI/dt = 100/3.3 = 33A/s^2

C'mon guys, you know this stuff and it's not that hard.

 

You cans also ask LTspice to plot the derivative of current i, with respect to t. That will give you an initial value which will decay toward zero.

 

so to find the initial rate you just do L/V ?

so to find the initial rate you just do L/V ?

Vr = I • R ohm's law
Vi = L • dI/dt definition of an inductor
Vt - Vr - Vi = 0 Kirchoff's law

Vt - I•R = L•dI/dt algebra
dI/dt = (Vt - I•R)/L = V/L at t=0 when I=0

dI/dt = 100/3.3 = 33A/s^2

C'mon guys, you know this stuff and it's not that hard.

Thank you