Question

A water molecule perpendicular to an electric field has 1.40×10−21 J more potential energy than a water molecule aligned with the field. The dipole moment of a water molecule is 6.2×10−30Cm.
What is the strength of the electric field?
Express your answer with the appropriate units.

Answer 1

Answer:

The strength of the electric field is 2.258 x 10⁸ N/C

Explanation:

Potential energy = -p*ECosθ

where;

d is the dipole moment

E is the electric field  

θ is the angle of inclination

→When the water molecules is perpendicular to the field, θ =90° and potential energy = p*ECosθ = d*ECos0 = 0

Total potential energy = 0 + 1.40×10⁻²¹J, since it is 1.40×10⁻²¹J more

→When the water molecules is aligned to the field, θ =0°

potential energy = -p*ECosθ

dipole moment, p = 6.2×10⁻³⁰Cm

                            = -(6.2×10⁻³⁰)*(E) Cos0

0 + 1.40×10⁻²¹ J = -(6.2×10⁻³⁰)*(E),

E = (1.40×10⁻²¹ J)/(6.2×10⁻³⁰)

E = 2.258 x 10⁸ N/C

Therefore, the strength of the electric field is 2.258 x 10⁸ N/C