Math Question

[chawalang]

Can someone please explain the exact math for this question.

This is from the ETCP practice questions.

Four 50w, 12v MR16 lamps are to be connected to a 48v transformer.

The math to where those lamps uses 1 amp or less, I am using A= w/v but I think I'm missing something, I am assuming it has to do with the transformer.

 

[jonliles]

Are the lamps connected in series or parallel? I would assume in series as 12V+12V+12V+12V=48V. What's the question you are trying to answer? What does it ask you to solve for?

twinkle, twinkle, little star, power = i^2 * r.

Also: I=V/(r1+r2+...+rn).

 

[derekleffew]

http://www.controlbooth.com/threads/amperage-of-series-circuit-mr16-eyc-lamps.25674/#post-226609 and posts following.

 

[chawalang]

Thanks, i was actually confusing myself with the math but it all makes sense now.

 

[JD]

In this case with equal lamps running at their rated voltage, total load is the shortcut:
200w/48v = 4.167 amps. (Rounded to 4) So, the transformer doesn't really play a role unless they ask for the primary draw
(in that case 200w/120v = 1.67 unless you want to be super exact and factor the transformer waste, assuming the primary is 120 and it's running off 120)

 

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