The magnetic field produced by a current flowing through a straight conductor is inversely proportional to the $........$.

$A$ circular loop placed in a plane perpendicular to the plane of paper carries a current when the key is $ON$. The current as seen from points $A$ and $B$ (in the plane of paper and on the axis of the coil) is anti-clockwise and clockwise respectively. The magnetic field lines point from $B$ to $A$. The $N-$ pole of the resultant magnet is on the face close to

Which is the direction of magnetic force acting on a current-carrying wire placed in a magnetic field?

The induced potential difference produced in a coil when a magnet is inserted into it does not depend upon:

$(a)$ What is the direction of magnetic field lines inside a bar magnet and outside of it?
$(b)$ What does the degree of closeness of the field lines represent?

Name three colours used and names of the wires used in household wiring.