On which principle is electricity generated in a power plant?

Name some devices in which electric motors are used.

State the rule to determine the direction of: $(i)$ a magnetic field produced around a straight current-carrying conductor,$(ii)$ force experienced by a current-carrying straight conductor placed in a magnetic field perpendicular to it,and $(iii)$ current induced in a coil due to its rotation in a magnetic field.

Which sources produce alternating current?

The principle of which of these devices is based on electromagnetism?

$(a)$ Magnetic field lines of two bar magnets $A$ and $B$ are as shown below. Name the poles of the magnets facing each other.
$(b)$ Two magnetic field lines never intersect each other. Why?
$(c)$ How does the strength of the magnetic field at the centre of a current-carrying circular coil depend on the
$(i)$ radius of the coil,
$(ii)$ number of turns in the coil, and
$(iii)$ strength of the current flowing in the coil?