When cell of E.M.F. '$E_1$' is connected to potentiometer wire the balancing length is '$l_1$'. Another cell of E.M.F. '$E_2$' ($E_1 > E_2$) is connected along with $E_1$ so as two cells oppose each other, the balancing length is '$l_2$'. The ratio $E_1 : E_2$ is

In the following network,
$I_1 = -0.4\,\text{A}$ , $I_4 = 1\,\text{A}$ , $I_5 = 0.4\,\text{A}$
The values of $I_2$, $I_3$ and $I_6$ are respectively

A particle of charge '$q$' and mass '$m$' moves in a circular orbit of radius '$r$' with angular speed '$\omega$'. The ratio of the magnitude of its magnetic moment to that of its angular momentum depends upon

A straight long wire is carrying current I. The ratio of magnetic field due to this wire at perpendicular distance 2 cm and 5 cm respectively from the wire is