The voltage induced in a coil by a changing flux will be of such a polarity that if a current could flow as a result of that induced voltage, the flux established by that current would oppose the original flux change. This is known as:

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?