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Time Constant Calculations
52 questions By Tony R. Kuphaldt
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Question 37 of 52
Determine the inductor voltage and inductor current at the specified times (time t = 0 milliseconds being the exact moment the switch contacts close):
Time VL (volts) IL (mA)
0 μs
10 μs
20 μs
30 μs
40 μs
50 μs
Reveal answer
Time VL (volts) IL (mA)
0 μs 20 0
10 μs 11.89 6.238
20 μs 7.069 9.947
30 μs 4.203 12.15
40 μs 2.499 13.46
50 μs 1.485 14.24
Notes:Be sure to have your students share their problem-solving techniques (how they determined which equation to use, etc.) in class.
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Question 38 of 52
Determine the inductor voltage and inductor current at the specified times (time t = 0 milliseconds being the exact moment the switch contacts close):
Time VL (volts) IL (mA)
0 ns
250 ns
500 ns
750 ns
1.00 μs
1.25 μs
Reveal answer
Time VL (volts) IL (mA)
0 ns 12 0
250 ns 6.110 21.82
500 ns 3.111 32.92
750 ns 1.584 38.58
1.00 μs 0.8065 41.46
1.25 μs 0.4106 42.93
Notes:Be sure to have your students share their problem-solving techniques (how they determined which equation to use, etc.) in class.
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Question 39 of 52
Complete this table of values for inductor voltage and current. Consider time = 0 to be the precise moment the switch closes:
Time (μs) VL (V) IL (mA)
0
50
100
150
200
250
300
350
400
Reveal answer
Time (μs) VL (V) IL (mA)
0 5.00 5.00
50 3.22 5.81
100 2.07 6.33
150 1.34 6.67
200 0.860 6.88
250 0.554 7.02
300 0.357 7.11
350 0.230 7.17
400 0.148 7.21
Notes:This circuit demands careful pre-analysis of the initial and final values. If students experience difficulty calculating the voltage and current figures here, it is probably due to incorrect initial and final values for voltage and/or current.
Maybe this will help someone else. The general formulas for V(t) and I(t) in question 25 (and the x(t) versions in question s 23 and 14) contain typos (or maybe hypertext coding glitches). They should actually be V(t) = (Vf-Vo)(1-e^(-t/𝛕)) + Vo, I(t) = (If-Io)(1-e^(-t/𝛕)) + Io in question 25. Those are correct in the PDF download version. In questions 23 and 24 the equations are x = xinitial + ( xfinal − xinitial ) ( 1 − e[(−t)/(τ)] ).