Which type of magnet is used in a crane to lift cars?

According to Fleming's right-hand rule,what is indicated by the direction of the center finger?

What are the factors on which the magnetic field due to a current carrying solenoid depends?

At the centre of which of the following four circular rings has the maximum magnetic field while passing equal current through each of them?

Give the factors on which the magnetic field produced by a current-carrying solenoid depends.

Draw the pattern of magnetic field lines associated with a current-carrying straight conductor. State how the magnetic field produced changes:
$(i)$ with an increase in current in the conductor,and
$(ii)$ with an increase in the distance from the conductor.