NCEES PE electrical and Computer practice exam 512

0.035+0.049j *(500/1000*2)

Why is it divided by 2 in the solution?

Rajan said:

0.035+0.049j *(500/1000*2)

Why is it divided by 2 in the solution?

Click to expand...

You say divided by, but have multiply in your equation. If it's multiply, it's more than likely this is calculating the impedance of a conductor. If the cable is single phase, you will want to multiply by 2 to take into account the impedance of the return path (the neutral conductor). This is not needed when calculating impedance for 3 phase conductors.

I'm assuming this is the NCEES practice problem where there are two conductors run in parallel because this question comes up often. 

What is the equivalent resistance of two identical resistors in parallel?

if: R1 = R2 = R

Then: Req = R//R

Req = (R*R)/(R+R)

Req = (R*R)/(2R)

Req = R/2

The value is halved. The same happens with conductors run in parallel. 

Each of the NCEES practice exam problems have been discussed to great length on engineer boards with multiple threads. You can find them easily by using the search function instead of making a new thread. For example, here are other threads discussing the same problem that I found using the search function: