Two wires A and B of equal lengths are connected in left and right gap respectively of a metre bridge, null point is obtained at 40 cm from left end. Diameters of the wires A and B are in the ratio 3:1 respectively, the ratio of specific resistance of A to that of B is

An iron rod is placed parallel to magnetic field intensity 2000 A/m. The magnetic flux through rod is $6 \times 10^{-4}$ wb and its cross sectional area is 3 cm$^2$. The magnetic permeability of the rod in wb/A-m is

The magnetic flux near the axis and inside the air core solenoid of length 60 cm carrying current I is $\dfrac{\pi}{2} \times 10^{-6}$ Wb. Its magnetic moment will be (cross-sectional area is very small as compared to length of solenoid, $\mu_0$ = Permeability of free space = $4\pi \times 10^{-7}$ SI unit)

If the number of turns in the coil of a moving coil galvanometer decreases, the resistance of the galvanometer,