Whats is em value for electrons ?
em value for electron is the ratio of charge on an electron to its mass.
Charge on an electron = 1.602 × 10−19 C.
Mass of an electron = 9.109 × 10−31 Kg.
Therefore,
em = 1.602× 10−19C9.109×10−31Kg
⇒ em = 1.602× 10−19C9.109×10−31Kg
⇒ em = 1.76 × 1011 C/kg