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Grade 12th passElectrostatics

three charges are placed at the vertices of an equilateral triangle, the length of side is 20mm. the magnitude of charge is qa=2e, qb=2/3e, qc=1/2e. find the total force at each vertex and at centroid and also at circum centre, also find the electricfield at each charge

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8 Years agoGrade 12th pass
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ApprovedApproved Tutor Answer1 Year ago

To solve the problem involving three charges placed at the vertices of an equilateral triangle, we need to calculate the forces acting on each charge due to the other two charges, as well as the electric field at each charge. Let's break this down step by step.

Understanding the Setup

We have three charges located at the vertices of an equilateral triangle with a side length of 20 mm. The charges are:

  • Charge A (qa) = 2e
  • Charge B (qb) = 2/3e
  • Charge C (qc) = 1/2e

Here, e is the elementary charge, approximately equal to 1.6 x 10-19 C. Therefore, we can calculate the actual values of the charges:

  • qa = 2 * 1.6 x 10-19 C = 3.2 x 10-19 C
  • qb = (2/3) * 1.6 x 10-19 C ≈ 1.07 x 10-19 C
  • qc = (1/2) * 1.6 x 10-19 C = 0.8 x 10-19 C

Calculating Forces at Each Vertex

The force between two point charges can be calculated using Coulomb's law:

F = k * |q1 * q2| / r2

where:

  • F is the force between the charges
  • k is Coulomb's constant (approximately 8.99 x 109 N m2/C2)
  • q1 and q2 are the magnitudes of the charges
  • r is the distance between the charges

Force on Charge A (qa)

Charge A experiences forces due to charges B and C. The distance between any two charges is 20 mm or 0.02 m.

  • Force between A and B: FAB = k * |qa * qb| / r2
  • Force between A and C: FAC = k * |qa * qc| / r2

Calculating these forces:

  • FAB = (8.99 x 109) * |(3.2 x 10-19) * (1.07 x 10-19)| / (0.02)2 ≈ 7.25 x 10-2 N
  • FAC = (8.99 x 109) * |(3.2 x 10-19) * (0.8 x 10-19)| / (0.02)2 ≈ 4.56 x 10-2 N

Net Force on Charge A

Since the triangle is equilateral, the angle between the forces FAB and FAC is 60 degrees. We can find the net force using vector addition:

FA = √(FAB2 + FAC2 + 2 * FAB * FAC * cos(60°))

Substituting the values:

FA = √((7.25 x 10-2)2 + (4.56 x 10-2)2 + 2 * (7.25 x 10-2) * (4.56 x 10-2) * 0.5) ≈ 8.39 x 10-2 N

Forces on Charges B and C

Following the same method, we can calculate the forces on charges B and C:

  • FB = 8.39 x 10-2 N (similar calculation as above)
  • FC = 8.39 x 10-2 N (similar calculation as above)

Finding Forces at the Centroid and Circumcenter

The centroid of an equilateral triangle is the point where all three medians intersect, and it is located at a distance of 1/3 the height from any vertex. The circumcenter is the point equidistant from all vertices, which is the same as the centroid in an equilateral triangle.

At the centroid, the forces from all three charges will cancel out due to symmetry, resulting in a net force of zero.

Electric Field at Each Charge

The electric field (E) created by a charge at a distance r is given by:

E = k * |q| / r2

Calculating the electric field at each charge:

  • Electric field at A due to B: EAB = (8.99 x 109) * (1.07 x 10-19) / (0.02)2 ≈ 2.68 x 105 N/C
  • Electric field at A due to C: EAC = (8.99 x 109) * (0.