I have a 9 Volt DC source in series with an inductor, and a switch. Once i close the switch, there is a spike on the screen of my oscilloscope but it is not precisely when I close the switch, a very breif moment later. The spike rapidly comes down to a steady line across the screen - indicating the dc source. Once I open the switch I get the reverse situation, the spike is in the negative and increases to the steady state.I am not truly understanding what is going on here. I connected my leads across the coil, negative to the side of the coil connected from the negative battery terminal, the positive to the other end. I am seeing the voltage drop across the coil, as the current increases is this voltage drop increasing to a maximum point then it suddenly returns to a minimum value where the voltage is source? I am soo confused .Help !!
I suppose coil is inducter you meanthen change of its inductive reactance will determine its change in voltage.since you are having dc source voltage will not change to maximum value when current change to max reason rate of change of current is 0 then. why did you ask 3 times hhhaaahh?
When you turn the current off, you are forcing the current to be zero in a short time. Since: V L x (rate-of-change of current), the voltage will go negative for the short time that the current changes from it's steady value to zero. When you turn the circuit on, you should initially see the full (open circuit) voltage of the battery. I imagine this is the spike you see. After a short time, the current reaches the battery's limit, and the voltage will drop. If the battery is fresh, you should see the spike at about 9V, and then it will drop to a steady value that is less than 9V. Current is being limited by the battery's internal resistance. Hope this helps.
Inductors inherently oppose changes in current. The way they do that is to induce a voltage, opposite in polarity with the applied voltage, in an attempt to keep the current the same. So you will get a spike of voltage when you apply power to the circuit, which is for a brief moment of time, stabilizing the current through the inductor. The value of the inductor will dictate the time in seconds, that the inductor will oppose the change in current. The bigger the inductor value, the more time it takes for the inductor to accept the change in current. Once the transients die off, the spike will die, and the inductor will accept its new current flow. This happens almost like a capacitor charging, but opposite.
