Inductor voltage calculation in time.

[amiras]

Homework Statement

This image gives all variables.

Homework Equations

Lets say that until second 1 the circuit was as it is. And and from 1 to 5 sec switch turned up, then from 5-6 turned down. Help me to calculate inductor voltage at these time intervals.
Please explain to me how to calculate voltage.

The Attempt at a Solution

I calculated the currents at those time intervals

t=1(sec), I = 2 A
t=5, I= 7.16 A
t=6, I=6,54 A

If i would try to draw a graph does voltage would go down all the time? And how to calculate the starting voltage?

 

[jbsteele]

To calculate the voltage across the inductor at any given time, you need to use the equation for the voltage across an inductor: V = L * dI/dt. The starting voltage is the voltage across the inductor just before the switch is closed (the initial current through the inductor is zero). At t=1 sec, the rate of change of current is 2 A/sec and the inductance is 0.2 H, so the voltage across the inductor is 0.4 V. At t=5 sec, the rate of change of current is 7.16 A/sec and the inductance is still 0.2 H, so the voltage across the inductor is 1.432 V. At t=6 sec, the rate of change of current is 6.54 A/sec and the inductance is still 0.2 H, so the voltage across the inductor is 1.308 V.