test question

[ddkeith]

I was takeing Mikes practice test on theory yesterday and came across a question that I can't come up with the right answer. The question reads, What is the power loss of a conductor that carries 24A and has a voltage drop of 7.2V?
A. 175W
B. 350W
C. 700W
D. 2,400W

The correct answer according to the the test is 175W but I keep coming up with 172.8W. Can somebody show me how to work this one out.

 

[spsnyder]

Given the choices I would pick A. It is the closest to 172.8 W.

 

[al hildenbrand]

The power lost in the conductor is the current passing through the conductor times voltage drop across the conductor. Or:

W = I * E = 24 Volts x 7.2 Amps = 172.8 Watts.

Now, if the Voltage had been 25 Volts and the current had been 7 Amps the calculation would have been exactly 175 Watts.

 

[ddkeith]

Thank you I just thought I was doing something wrong by not getting 175W.

 

[ddkeith]

could that have been a error on the question.

 

[al hildenbrand]

could that have been a error on the question.

That depends upon the test instructions.

In my opinion, you could question the test giver.

There can be simple rules about accuracy and rounding that might apply.

 

[al hildenbrand]

Thank you.

Oh, and, you're welcome. :smile:

 

[LarryFine]

Now, if the Voltage had been 25 Volts and the current had been 7 Amps the calculation would have been exactly 175 Watts.

True, and the same would be true if the current was 25a and the voltage drop was 7v.

 

[al hildenbrand]

..............