e.m.f. can be induced in a circular coil by(1 Point)all of thesethe area of the coil becomes greater.a stronger magnet is used.increasing the number of turns.

The electromagnetic force (e.m.f.) can be induced in a circular coil by all of the following methods:

1. Increasing the area of the coil: A larger coil area can capture more of the magnetic field, which can induce a greater e.m.f.

2. Using a stronger magnet: The strength of the induced e.m.f. is directly proportional to the strength of the magnetic field. Therefore, using a stronger magnet can induce a greater e.m.f.

3. Increasing the number of turns in the coil: The e.m.f. induced in a coil is directly proportional to the number of turns in the coil. Therefore, increasing the number of turns can induce a greater e.m.f.

So, the answer is "all of these".