Solving Transformer Problems: Primary and Secondary Coils

[kkarapet]

Transformer problem, Please Help!

Please help with this problem.

A transformer consists of 300 primary windings and 804 secondary windings.
a) If the potential difference across the primary coil is 21.0 , what is the voltage across the secondary coil ?
Found this part, Vs = 56.3 V

b) If the potential difference across the primary coil is 21.0 V , what is the effective load resistance of the secondary coil if it is connected across a 145 Ohms resistor?

This part I am not getting. Is it saying that 145 Ohms is Rp (Resistance of the primary coil) ??, or there are more than one resistors for the secondary coil and I need to find the Req. Please help!

Homework Statement

 

[rude man]

Probably they mean what resistance is reflected back to the primary winding. In other words, what resistance does the 21V source see?

You can deduce the answer from an energy-conservation argument.

 

[kkarapet]

Thank you!