Question

a point charge q having mass m is held stationary with the help of an electric field write an expression for E in terms of m and q​

Answer 1

In the Given Question, It is written that the Particle which is charged is help stationary in the electric flied this means that there are some extra forces which is opposing the force of the electric filed. As a result of which the Particle is held stationary.

Now, there is no force which is given in question, other than that of Electric filed. But note, that there is an hint in question, that hint is that mass of the charge is given, which directly means that the gravitational force of the attraction is must balancing the electrostatic force.

Now, Writing the mathematical equation of the force.

  F of gravity  = F of electrostatics.

  ∴ mg = qE

   E = mg/q

Now, This is the Required expression for your question.

Hope it helps.