The resistances of three parts of a circular loop are as shown in the figure. The magnetic field at the centre $O$ is:

$A$ wire $A$, bent in the shape of an arc of a circle, carrying a current of $2 \, A$ and having radius $2 \, cm$, and another wire $B$, also bent in the shape of an arc of a circle, carrying a current of $3 \, A$ and having radius $4 \, cm$, are placed as shown in the figure. The ratio of the magnetic fields due to the wires $A$ and $B$ at the common centre $O$ is

The magnetic field induction at the centre of a circular coil of radius $5 \,cm$ carrying a current of $0.9 \,A$ is (in $SI$ units) (where $\varepsilon_0$ is the absolute permittivity of air in $SI$ units, and the velocity of light $c = 3 \times 10^8 \,ms^{-1}$):

Six very long insulated copper wires are bound together to form a cable. The currents carried by the wires are $I_1 = +10 \text{ A}, I_2 = -13 \text{ A}, I_3 = +10 \text{ A}, I_4 = +7 \text{ A}, I_5 = -12 \text{ A}$ and $I_6 = +18 \text{ A}$. The magnetic induction at a perpendicular distance of $10 \text{ cm}$ from the cable is (Given: $\mu_0 = 4\pi \times 10^{-7} \text{ T m/A}$) (in $\mu\text{T}$)

Which of the following statements is true regarding magnetic lines of force?

Which of the following is a vector quantity?