Figure shows a potentiometer wire AB having resistance of $5\ \Omega$ and length 10 m. An e.m.f. is $0.4$ V of battery, the balancing length AP is (internal resistance is negligible)

The currents in different parts of the electric circuit are shown in following figure. The value of current $i$ is

An electron is moving with initial velocity $\vec{v} = V_0\hat{j}$ in a magnetic field $\vec{B} = B_0\hat{i}$. Its de-Broglie wavelength will

A thin circular wire carrying current $I$ has magnetic moment $M$. The shape of the wire is changed to a square and it carries the same current. It will have magnetic moment $M_1$. The ratio $M$ to $M_1$ is