$A$ long straight wire carrying a constant current $i$ is placed in the same plane as a rectangular loop of length $l$. The distance of the sides of the loop from the wire are $r_1$ and $r_2$. If the area under the curve of the magnetic field $B$ versus distance $r$ graph between $r_1$ and $r_2$ is $A$,find the magnetic flux through the loop.

Explain the concept of magnetic flux.

$A$ flux of $1 \ mWb$ passes through a strip having an area $A = 0.02 \ m^2$. The plane of the strip is at an angle of $60^{\circ}$ to the direction of a uniform field $B$. The value of $B$ is

$(a)$ Magnetic field lines show the direction (at every point) along which a small magnetised needle aligns (at the point). Do the magnetic field lines also represent the lines of force on a moving charged particle at every point?
$(b)$ Magnetic field lines can be entirely confined within the core of a toroid,but not within a straight solenoid. Why?
$(c)$ If magnetic monopoles existed,how would the Gauss's law of magnetism be modified?
$(d)$ Does a bar magnet exert a torque on itself due to its own field? Does one element of a current-carrying wire exert a force on another element of the same wire?
$(e)$ Magnetic field arises due to charges in motion. Can a system have magnetic moments even though its net charge is zero?

$A$ square of side $x \, m$ lies in the $x-y$ plane in a region where the magnetic field is given by $\vec B = B_0 (3\hat i + 4\hat j + 5\hat k ) \, T$,where $B_0$ is a constant. The magnitude of the magnetic flux passing through the square is:

The adjoining figure shows two different arrangements in which two square wire frames are placed in a uniform constantly decreasing magnetic field $B$. The value of magnetic flux in each case is given by: