An ideal transformer is needed to step the voltage down from 400V to 115V. The primary has 400 turns. How many turns would be necessary on the secondary side?

Np/Ns = Vp/Vs,

400/Ns = 400/115,
Ns = 115 = Turns on secontary winding.

To determine the number of turns required on the secondary side of an ideal transformer to step the voltage down from 400V to 115V, we can use the voltage ratio equation for transformers:

(Vp / Vs) = (Np / Ns)

Where:
Vp = primary voltage
Vs = secondary voltage
Np = number of turns on the primary side
Ns = number of turns on the secondary side

In this case, Vp is 400V and Vs is 115V, and Np is given as 400 turns. We need to find Ns.

So, we can rearrange the equation to solve for Ns:

Ns = (Np * Vs) / Vp

Substituting the given values:

Ns = (400 * 115) / 400

Simplifying further:

Ns = 46

Therefore, 46 turns would be necessary on the secondary side to step the voltage down from 400V to 115V.