Question

The electric field intensity just sufficient to balance the earth’s gravitational attraction on an electron will be:

• A. \( -5.6 \times 10^{-11} \, \text{N/C} \)
• B. \( -4.8 \times 10^{-15} \, \text{N/C} \)
• C. \( -1.6 \times 10^{-19} \, \text{N/C} \)
• D. \( -3.2 \times 10^{-19} \, \text{N/C} \)

Hint:

To balance gravitational force on an electron, the electric field intensity must equal \( mg/e \).

Answer 1

The Correct Option is A

Step 1: Balance of forces.
The force due to gravity on an electron is \( F_g = mg \), and the force due to electric field is \( F_e = eE \). To balance the gravitational force, we set: \[ mg = eE \] where \( m \) is the mass of the electron, \( g \) is the acceleration due to gravity, and \( e \) is the charge of the electron.

Step 2: Solve for electric field intensity.
Substitute the values of \( m = 9.1 \times 10^{-31} \, \text{kg} \), \( g = 9.8 \, \text{m/s}^2 \), and \( e = 1.6 \times 10^{-19} \, \text{C} \) to get the electric field intensity \( E = 5.6 \times 10^{-11} \, \text{N/C} \). Thus, the correct answer is (1).