A potentiometer wire is 4m long and potential difference of 3V is maintained between the ends. The e.m.f. of the cell which balances against a length of 100 cm of the potentiometer wire is

A metre bridge experiment, the resistance in the left gap is $20\ \Omega$ and in the right gap is $60\ \Omega$. The bridge is balanced. The distance of the null point from the centre of the wire is

The magnetic moment produced in a sample of 2 gram is $8 \times 10^{-7}\,\text{A/m}^2$. If its density is $4\ \text{g/cm}^3$ then the magnetization of the sample is

A wire carrying current 'I' along x axis has length 'L' and it is kept in a magnetic field $B(\hat{i}+2\hat{j}-2\hat{k})$ T. The magnitude of magnetic force acting on the wire is