What is the shape of the magnetic field lines around a circular current-carrying conductor?

The figure below shows a current-carrying loop passing through a sheet of cardboard. Draw three magnetic field lines on the cardboard.
Give two factors on which the magnitude of the magnetic field at the centre of the loop depends.

$(a)$ Name the type of electric current generated by most of the power stations in our country.
$(b)$ Why is it preferred over the other type?
$(c)$ State the frequency of the power supply generated in India.

Choose the incorrect statement from the following regarding magnetic field lines.

$(a)$ What is an electromagnet? What does it consist of?
$(b)$ Name one material in each case which is used to make a: $(i)$ permanent magnet $(ii)$ temporary magnet.
$(c)$ Describe an activity to show how you can make an electromagnet in your school laboratory.

$A$ magnet is moved towards a coil,an $emf$ and charge are induced in it. If the magnet is moved slowly,how will the new $emf$ and charge be affected?