8. An electron of mass m is kept in a vertical electric field of magnitude E. What must be the value of E so that the electron doesn’t fall due to gravity? a) m*g*e b) e(m∗g) c) (m∗g)e d) 1(m∗g∗e)
Answer: c Explanation: Gravitational force on the electron is m*g (weight of the electron). Electrical force on the body is e*E. If the electron doesn’t fall then these two forces balance each other, so m*g=E*e. Therefore E= (m∗g)e.
