$A$ soft iron bar is introduced inside a current-carrying solenoid. The magnetic field inside the solenoid:

In the below figure,$A$ and $B$ represent two straight wires carrying equal currents in a direction at right angles to the plane of paper inwards. Sketch separately the magnetic field lines produced by each current. Give a reason why the magnetic field at $K$ (mid-point of the line joining $A$ and $B$) will be zero.
What will be the effect on the magnetic field at $K$ if the current in wire $B$ is reversed?

State Faraday's first law of electromagnetic induction.

$A$ coil of insulated wire is connected to a galvanometer. Explain what happens if a bar magnet with its north pole towards one face of the coil is:
$(i)$ moved quickly towards the coil,
$(ii)$ kept stationary inside the coil,and
$(iii)$ moved quickly away from the coil?

$(a)$ 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.

How does the magnetic field produced by a current-carrying straight wire vary with the distance from the wire?