Typically a transformer is connected on the primary side to a fixed source of em
ID: 1560498 • Letter: T
Question
Typically a transformer is connected on the primary side to a fixed source of emf, such as a generator and the current that is drawn on the primary side is set by the load on the secondary side. Let's call the primary emf V_p. For a particular application, the device that is to run on the secondary side is a fixed ohmic resistor R. If the number of turns on the primary and secondary coils are N_p and N_s, respectively, and no losses in the transformer, (A) express the primary and secondary currents/_p and l_s in terms of the constants R and V_p and the "turn ratio" N_p/N_s, thus showing that both the primary and secondary currents are determined by parameters on the two sides of the transformer. (B) What happens to l_s and V_s if the previous transformer is swapped for one with twice as many turns on the secondary side? Did/_s and V_s both change the same way and do the changes violate energy conservation?Explanation / Answer
a) Np/ Ns= Vp/Vs= Is/ Ip
Vs= Is R
Ip = ( Is) ( Ns/ Np) = Vs/ R ( Ns/Np)= (Vp) ( Ns/Np)^2 / R
Is= (Vs/) / R = ( Vp) ( Ns/Np) / R
b) N= 2Ns
Np/N = Vp/ V
Np/ 2Ns = Vp/ V
Np/ Ns = 2Vp/ V
Vp/ Vs= 2Vp/ V
V = 2Vs ( therefore secondary voltage becomes twice,
Is= V/ R = 2Vs/ R = therefore current will also become twice
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