How can it be shown that a magnetic field exists around a wire through which a direct current is passing?

By increasing the number of turns $3$ times in a toroidal solenoid,the magnetic field:

How does a current-carrying solenoid behave?

Which of the following appliances does not have a lower power rating?

$(a)$ Draw magnetic field lines of a bar magnet. "Two magnetic field lines never intersect each other". Why?
$(b)$ An electric oven of $1.5 \, kW$ is operated in a domestic circuit $(220 \, V)$ that has a current rating of $5 \, A$. What result do you expect in this case? Explain.

$(a)$ Electric fuse is an important component of all domestic circuits. Why?
$(b)$ An electric oven of rating $2 \, kW, 220 \, V$ is operated in a domestic circuit with a current rating of $5 \, A$. What result would you expect? Explain.