5/26 LR Circuits

We began class with the discussion of current verses time, and we found that as current changes over time it induces EMF in the inductor.

Our first activity is to calculate inductance given a number of turns in a coil, the area and resistance. We found the inductance to be 760 micro henry's. We also discussed engineering notation which uses 10^-6 for values.

Using the inductance we calculated above we were able to calculate resistance is an 18 gauge coil. Which resulted in .48 ohms.

Finally, using the inductance and resistance we were able to calculate our time constant, using the equation tao= L/R.

Using the oscilloscope, we experimentally calculated our inductance, which we used to compare to our theoretical value of 760 micro henry's.

Using the graph from the oscilloscope, we calculated our experiment inductance.

Our experimental value for inductance was 703 micro henrys. We had a 7.5 % error.

In our next activity, did a LR circuit problem, in which there are two resistors in parallel and one resistor is in series with an inductor. Using the inductor and resistor 1, we were able to calculate the the time constant using the time constant formula. Our time constant was 2.9E-4.

Using ohms law, we were able to calculate Imax, and used that to calculate the current (picture above).

Using the value for current from the pervious picture we were able to find the time.