Question Details

Net electric field at point A as shown in figure is at an angle of 60 with x-axis. Find P2 /P1 .


Options

A

1 3

B

2 3

C

3

D

3 2

Show Answer

Correct Answer :

Option B

2 3

Solution :

The correct answer is:
2 3

Step-by-Step Explanation:

1. Identify the dipoles and point A from the image:
From the given diagram, we have two short dipoles placed at the origin:
- Dipole 1 has a dipole moment vector P1 pointing in the negative x-direction (leftward), so:
P1 = - P1 i^
- Dipole 2 has a dipole moment vector P2 pointing in the positive y-direction (upward), so:
P2 = P2 j^
Point A lies on the positive x-axis at a distance r from the origin.

2. Electric field due to Dipole 1 at point A:
Since point A lies along the axis of dipole 1, the electric field is in the axial position. The axial electric field of a dipole is directed parallel to the dipole moment vector:
E1 = 1 4 π ε0 2 P1 r3 = - 2 k P1 r3 i^
where k=14πε0.

3. Electric field due to Dipole 2 at point A:
Since point A lies on the perpendicular bisector (equatorial line) of dipole 2, the electric field is in the equatorial position. The equatorial electric field of a dipole is directed opposite to the dipole moment vector:
E2 = - 1 4 π ε0 P2 r3 = - k P2 r3 j^

4. Net electric field at point A:
The net electric field vector Enet is the vector sum of both fields:
Enet = E1 + E2 = - 2 k P1 r3 i^ - k P2 r3 j^

5. Angle of the net electric field with the x-axis:
Since both the x and y components of the electric field are negative, the net field points into the third quadrant. The magnitude of the angle θ it makes with the x-axis is given by:
tan θ = | Ey Ex |
Substituting the values of Ex and Ey:
tan ( 60 ) = ( k P2 r3 ) ( 2 k P1 r3 )
Simplifying the ratio:
3 = P2 2 P1
Solving for the ratio P2P1:
P2 P1 = 2 3

Unlock Our Free Library

Access expert-curated educational resources and study materials—completely free.

Discover more resources

You may also like

Mock Tests

View All
  • JEE
  • intermediate
  • 3 hours
  • chemistry, mathematics, physics
  • Proctored

  • JEE
  • intermediate
  • 3 hours
  • chemical engineering, mathematics, physics

Ask AI Tutor
5 left
Q1 View Question & Options
AI Tutor is solving this question...
Reading question context & options...