Knowing which formula to use and how to use it is critical to effectively answering calculation related question on master and journeyman electrical exams.
Which formula would you use to answer the following question:
When the alternating current is given as 45 amperes, what is the maximum value of the current in a cycle?
Solution:
Step #1
Identify the required formula:
I maximum = I effective x ?2
I maximum = maximum current
I effective = effective current
Step #2
Identify I effective = 45 amps
Step #3
Identify constant required to convert I maximum to I effective:
The constant of 1.414 or the ?2, which is not provided in the text of the question, will convert effective current into maximum current.
Step #4
Plug values into equation and solve for the answer:
I (maximum current) = I (effective current) x ?2
= 45 amperes x ?2
= 45 amperes x 1.414
= 64 amperes
Understanding the difference between how maximum verses effective current operates in an AC system as well as how to apply the use of the constant 1.414 or the ?2 is the key to arriving at the correct answer.
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