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AMG38
AMG38
1 year ago

The current profile through the coil with the resistor Ri can be described with the following function:

For t=0, the current i (t)=0A is also. The coil acts as a very high resistance in the turn-on eye view.

Then the current rises. For the further course you need the time constant Tau. This results from:

For t, the coil in the direct current circuit then acts as a wire connection because the di/dt=0. The current i(t) is then only Uq/Ri.

At this point, however, the description of the task is somewhat unclear because it is not clearly defined whether the resistor R has previously been switched on and is active at t against infinitely. In the case, the current i(t) = Uq / (Ri + R)

In the case of task part b), the second resistor is connected in series at t=2s. As a result, the total resistance of the circuit changes and therefore also the time constant as well as the equation for the current.

For the time constant tau_b, you also pack the additional resistor R into the first equation of tau.

In task part c, it is a matter of the fact that the second resistor should not effect a subsequent change in the current level by switching on. This can only happen if it is already connected from the start.

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Doktorelektrik
Doktorelektrik
1 year ago

Just start. The first tasks are extremely simple and detachable in the head:

  • What current flows at t=0? Auxiliary question: where is the voltage?
  • If you only have switch 1 closed and wait a long time, which voltage is then applied to (each) coil in your dc circuit?

To do this, please consider the electrical effect of a coil on the electrical current (this is the learning goal to deal with it).

Good luck!

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