What will be the frequency of an alternating current if its direction changes after every $0.01\,s$ (in $,Hz$)?

Inside a current carrying solenoid,the magnetic field lines are:

How is alternating current $(AC)$ different from direct current $(DC)$?

If field lines of a magnetic field are crossed at a point,what does it indicate?

What is the nature of the magnetic field lines passing through the center of a current-carrying circular loop?

In the diagrams shown below:
$(i)$ Name the type of current in two cases.
$(ii)$ Identify any one source for each type of these currents.
$(iii)$ What is the frequency of current in case $(ii)$ in India?
$(iv)$ Use above graphs to write two differences between the current in two cases.