# The voltage across the secondary winding is 10,000 V, and the voltage across the primary winding is 25,000 V. lf the primary winding has 200 coils, how many coils are in the secondary winding?

Jun 2, 2017

The number of coils is $= 80$ coils

#### Explanation:

The equation for a transformer is

${V}_{s} / {V}_{p} = {n}_{s} / {n}_{p}$

The secondary voltage is ${V}_{s} = 10000 V$

The primary voltage is ${V}_{p} = 25000 V$

This is a step-down transformer.

The number of coils in the primary windings ${n}_{p} = 200$

The number of coils in the secondary windings is

${n}_{s} = {V}_{s} / {V}_{p} \cdot {n}_{p}$

$= \frac{10000}{25000} \cdot 200 = 80$ coils

Jun 2, 2017

80 turns

#### Explanation:

$\frac{{V}_{s}}{{V}_{p}} = {N}_{s} / {N}_{p}$
where:
${V}_{s}$ = Voltage of secondary coil
${V}_{p}$ = Voltage of primary coil
${N}_{s}$ = Turns at secondary coil
${N}_{p}$ = Turns at primary coil

Therefore:
$\frac{10000}{25000} = {N}_{s} / 200$
${N}_{s} = 80$ turns of wire