Physics

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A transformer consists of 275 primary windings and 834 secondary windings. If the potential difference across the primary coil is 25 V, (a) What is the voltage across the secondary coil? (b) what is the effective load resistance of the secondary coil if it is connected across a 125 ohm resistor.

Ok I got part (a) as being 75.82 V...but I am totally confused on part b I don't know what it is asking for or any equation that would work for it! Help please!

  • Physics -

    I suppose maybe they mean what is the resistance you will see on the primary side.
    Now the power on the secondary side is
    P = V^2/R = (75.8)^2 / 125
    P = 46 watts
    Now I suppose we assume a perfect transformer so we put in that 46 watts on the primary side
    46 = 25^2/R
    R = 625/46 = 13.6 ohms

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