Step-up transformer: find turns ratio and primary current

[crosbykins]

Homework Statement

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

Homework Equations

P primary = P seconary

Vp/Vs = Is/Ip = Np/Ns

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

 

[kuruman]

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

 

[crosbykins]

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

-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...

 

[kuruman]

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

 

[crosbykins]

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

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

 

[kuruman]

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