विद्युत जनरेटर (Electric generators) मुख्य रूप से निम्नलिखित में से किस वैज्ञानिक सिद्धांत के आधार पर कार्य करते हैं?

A step-down transformer connected to an AC mains supply of 220 V operates an 11 V, 44 W lamp. Ignoring power losses, what is the current in the primary circuit?

A transformer has 200 turns in its primary winding and 1000 turns in its secondary winding. What type of transformer is this?