What does the direction of the thumb indicate in the right-hand thumb rule?

What is the frequency of $220 \ V$ $DC$ voltage? (In $Hz$)

What are magnetic field lines? How is the direction of magnetic field at a point determined? Mention two important properties of magnetic field lines.

An alternating electric current has a frequency of $50 \, Hz$. How many times does it change its direction in one second? Give reason for your answer.

$(a)$ State the function of a fuse in an electric circuit. How is it connected in the domestic circuit?
$(b)$ An electric fuse of rating $3 \, A$ is connected in a circuit in which an electric iron of power $1.5 \, kW$ is connected,which operates at $220 \, V$. What would happen? Explain.

With the help of a labelled circuit diagram,illustrate the pattern of field lines of the magnetic field around a current-carrying straight long conducting wire. How is the Right-Hand Thumb Rule useful to find the direction of the magnetic field associated with a current-carrying conductor?