The mass and charge of an electron are m and e respectively. The momentum acquired by the electrons in l cm of wire when a current i starts to flow is

If α be the area of cross-section of wire, then its volume is a l. Let n be the number of electrons per unit volume. Now, the number of electrons in the wire is n a L The mass of the electron is m and if its drift velocity be vd, then momentum acquired by the electrons is the momentum acquired by the wire. So, momentum acquired by the wirep=nalmvdWe know that vd=i/nae∴ p=nalm(i/nae)or p=mile