Two charges Q1 = q and Q2 = mq are placed at the points P1(a, b) and P2(ma, mb), respectively, in the X Y plane, where a, b ≠ 0 and m ≠ 0, 1. If V1 is the potential at a point in the X Y plane due to charge Q1 and V2 is the potential at that point due to charge Q2. Correct statement(s) for the points at which |V1| = |V2| is/are:
Correct Answer :
For m = -1, locus of these points is ax + by = 0.
For m = 2, the locus of these points is a circle of radius centered at .
Solution :
The correct options are:
1. For m = -1, locus of these points is ax + by = 0.
2. For m = 2, the locus of these points is a circle of radius centered at .
Step 1: Express the condition for electric potential magnitude.
Let any arbitrary point in the XY-plane be (x, y).
The distance of (x, y) from point P1(a, b) carrying charge Q1 = q is given by:
Similarly, the distance of (x, y) from point P2(ma, mb) carrying charge Q2 = mq is given by:
The electric potential due to a point charge Q at a distance r is .
We are given that , which leads to:
Squaring both sides gives the general equation for the locus:
Step 2: Case 1: Analyze for m = -1
Substitute m = -1 into the distance condition :
Expanding both sides:
Simplifying by canceling common terms :
Hence, for m = -1, the locus is a straight line given by ax + by = 0.
Step 3: Case 2: Analyze for m = 2
Substitute m = 2 into the squared distance equation:
Expanding both sides:
Rearranging all terms to one side:
Dividing by 3:
Completing the squares for x and y:
This represents a circle centered at with radius .
Thus, both the statement for m = -1 and the statement for m = 2 are fully verified.
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