What physical effect allows a transformer to transfer energy between coils?

State the ideal transformer voltage ratio.

Does a step-up transformer increase or decrease current in the ideal model?

A transformer has \(N_p=200\), \(N_s=1000\), and \(V_p=24\,\mathrm V\). Find \(V_s\).

An ideal transformer has \(V_p=240\,\mathrm V\), \(V_s=12\,\mathrm V\), and \(I_s=5.0\,\mathrm A\). Find \(I_p\).

A transformer steps \(120\,\mathrm V\) up to \(480\,\mathrm V\). If the primary has \(150\) turns, find the secondary turns.

A real transformer takes \(500\,\mathrm W\) from the primary and delivers \(450\,\mathrm W\) to the secondary. Find its efficiency.

Why does an ideal transformer not work with steady DC?

An ideal transformer has turns ratio \(N_s/N_p=4.0\). A \(10\,\Omega\) load is connected to the secondary. What effective resistance is seen by the primary?

Derive the ideal transformer current ratio from the voltage ratio and conservation of power.