WECA HW Question Help

[Matt26]

What is the total current draw on a 120v system with recessed fluorescent luminaires rated 768W/806VA?
I got the question wrong with an answer of 6.4 (768/120=6.4). The right answer was 6.7 - assuming 806/120?)
Amps = watts divided by volts. What am I missing? Thanks! This is a self paced course so I do not have an instructor to ask... Will be asking my coworkers (electricians) about this but wanted to see what the internet has.

 

[Julie.]

The clue is in the terminology.
806VA (V = volts, A = amps)

So if the volts x amps = 806 and the volts is 120

I = 806/120.

Where do you get Watts = volts x amps?

What about the power factor in an ac circuit? - which may be the next question (768/806) btw

 

[James]

The relationship between watts, volts and amps is taught in schools .

however to simplify things, they only really discuss small DC circuits and for that the W = V x A formula is of course correct.

 

[Julie.]

The relationship between watts, volts and amps is taught in schools .

however to simplify things, they only really discuss small DC circuits and for that the W = V x A formula is of course correct.

Weca is a US (california) trade organisation, similar to nappit - but has assessment exams for electricians and electrical engineers, essentially the same as an 18th edition exam it isn't a school level knowledge.

The majority of the questions are about code (regulations) applicable to california and the US in general.

So similar to our 18th - such as "how many receptacles (socket outlets) on a branch (spur)? - answer unlimited!! (One)

So anyone looking at qualifying should definitely know the differences between ac and dc calculations