K.C.S.E Physics Q & A - MODEL 2014PP2QN15

K.C.S.E Physics Q & A - MODEL 2014PP2QN15

​(a) One of the causes of energy loss in a transformer is heating in the coils when current flows. State:
(i)the reason why the current causes heating. 
(ii) how the heating can he minimized. 
(b) The input voltage of a transformer is 240 V and its output is 12 V. When an 80 W bulb is connected across the secondary coil, the current in the primary coil is 0.36 A

​Determine:
(I) the ratio Np/Nsof the transformer, (where Np is the number of turns in the primary coil and Ns is the number of turns in the secondary coil) 
(ii) the power input of the transformer. 
(iii) the power output of the transformer. 
(iv) the efficiency of the transformer. 

answers

​(a) (i) resistance in the coils.
(ii) use of thicker copper wires.