Calculating Characteristics of a Step-Up Transformer

We solve $\frac{V_{\text{s}}}{V_{\text{p}}}=\frac{N_{\text{s}}}{N_{\text{p}}}$ for $N_{\text{s}}$, the number of loops in the secondary, and enter the known values. This gives

A large number of loops in the secondary (compared with the primary) is required to produce such a large voltage. This would be true for neon sign transformers and those supplying high voltage inside TVs and CRTs.

We can similarly find the output current of the secondary by solving $\frac{I_{\text{s}}}{I_{\text{p}}}=\frac{N_{\text{p}}}{N_{\text{s}}}$ for $I_{\text{s}}$ and entering known values. This gives

As expected, the current output is significantly less than the input. In certain spectacular demonstrations, very large voltages are used to produce long arcs, but they are relatively safe because the transformer output does not supply a large current. Note that the power input here is . This equals the power output , as we assumed in the derivation of the equations used.