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Inductive Reactance
13 questions By Tony R. Kuphaldt
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Question 7 of 13
An inductor rated at 4 Henrys is subjected to a sinusoidal AC voltage of 24 volts RMS, at a frequency of 60 hertz. Write the formula for calculating inductive reactance (XL), and solve for current through the inductor.
Reveal answerXL = 2 πf L The current through this inductor is 15.92 mA RMS.
Notes:I have consistently found that qualitative (greater than, less than, or equal) analysis is much more difficult for students to perform than quantitative (punch the numbers on a calculator) analysis. Yet, I have consistently found on the job that people lacking qualitative skills make more “silly” quantitative errors because they cannot validate their calculations by estimation.
In light of this, I always challenge my students to qualitatively analyze formulae when they are first introduced to them. Ask your students to identify what will happen to one term of an equation if another term were to either increase, or decrease (you choose the direction of change). Use up and down arrow symbols if necessary to communicate these changes graphically. Your students will greatly benefit in their conceptual understanding of applied mathematics from this kind of practice!
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Question 8 of 13
At what frequency does a 350 mH inductor have 4.7 kΩ of reactance? Write the formula for solving this, in addition to calculating the frequency.
Reveal answerf = 2.137 kHz
Notes:Be sure to ask your students to demonstrate the algebraic manipulation of the original formula, in providing the answer to this question. Algebraic manipulation of equations is a very important skill to have, and it comes only by study and practice.
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Question 9 of 13
How much inductance would an inductor have to possess in order to provide 540 Ω of reactance at a frequency of 400 Hz? Write the formula for solving this, in addition to calculating the frequency.
Reveal answerL = 214.9 mH
Notes:Be sure to ask your students to demonstrate the algebraic manipulation of the original formula, in providing the answer to this question. Algebraic manipulation of equations is a very important skill to have, and it comes only by study and practice.
