CTS Sample Question of the Week: Feb 24, 2025
A wall mounted assistive listening system transmitter has its 12 V, 1.8 A, DC power supply remotely located in the AV rack 25 feet away. What is the voltage drop attributable to the 18 AWG power extension wire used which has a resistance of .0062 ohms per foot, and will this be within a 5% voltage operating tolerance for the ALS transmitter?
a. 1.86 volts and is in tolerance
b. 0.558 volts and is in tolerance
c. 1.86 volts and is out of tolerance
d. 0.558 volts and is out of tolerance
Which do you think is the best answer? Post your choice below and check back Friday to see if you got it right.
Update: The correct answer is - b. 0.558 volts and is in tolerance
How did you do? Come back Monday for another question!
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For questions like this that are math related, it would be very helpful if you showed the work as to how you came to the answer, or to reference the section in the exam guide where the formula could be found. I posed this question to several people - some CTS holders, some not yet - and the best anyone could do was to take a guess. No one could come up with the formula or reasoning behind the math, nor could anyone find the answer in the guide.
I strongly agree with you, Jeff!
So, I had made an error in my calculations which is why I chose C.
To get their answer, voltage drop = amps * (2 * length * resistance), then figure percentage of drop to figure out tolerance or not.