In single phase energy meter, Current coil is made up from thick wire having few no. of turns. Pressure coil is made up from thin wire having more no. of turns.
Where, d is distance in m Q is value of variable resistor in ohm P is variable resistance in ohm Here Q/P = 1/3 is given, d = Q/(P + Q)*Loop length = 1/4*(2*600) = 300 m