Name the coil of which the wire is thicker in a (i) step up, (ii) step down transformer. Give a reason for your answer.
1) A transformer which increases the voltage is called a step-up transformer. K>1 or Ns > Np. Since the secondary current is less than the primary current, the primary coil is made up of thick wire to sustain high current.
2) As you say, Step Down Transformer, It step-downs the voltage at constant power.
This, in turn, increases the secondary current. For higher Current Rating, we need a thicker conductor. The thicker conductor also helps to reduce I²R losses as thicker the conductor, lower the resistivity.
P = V x I
as V decreases, I increase for the power to remain constant.
P —-> Total power
V —→ Voltage
I —→ Current
In contrast, the step-up transformer has thinner conductors in Secondary and thicker conductors in the primary, for the same reason