Transformer qs, find turns ration & primary current

1. May 17, 2010

crosbykins

1. The problem statement, all variables and given/known data
A step up transformer is designed to operate from a 12V supply and to deliver energy at 240V. If the secondary winding is connected to a 60W, 240 V lamp, determine:

a) the turns ratio of the transformer
b) the primary current

2. Relevant equations

P primary = P seconary

Vp/Vs = Is/Ip = Np/Ns

3. The attempt at a solution
-ok...well, I don't know how to do this at all, my textbook only had really straight forward questions where the info for primary and secondary was directly given...please help

2. May 17, 2010

kuruman

First question to answer: Is this a step-up or step-down transformer?

3. May 17, 2010

crosbykins

-it's a step up

that means Vp is less than Vs, but Ip is greater than Is

i don't know how to identify the P, Vp, Vs from the info...

4. May 17, 2010

kuruman

What is hooked up to the power supply is the primary. So what is Vp?

5. May 17, 2010

crosbykins

so Vp is 12V and than I guess Vs is 240V and P is 60W.

6. May 17, 2010

kuruman

Can you find the turns ratio now? What about the current in the primary?