Physics Electrostatics MDCAT 2017
PMDC Verified Question 112 of 131
Q.91 A point charge at a distance 'x' from another point charge experiences a force of repulsion, which one of the following graphs shows. How the force is related to 'x':

Force (F) Distance (x) F vs x
A
Straight line with negative slope
B
Inverse square curve (hyperbola-like decay)
C
Straight line with positive slope through origin
D
Straight line with negative slope starting from y-axis
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: Inverse square curve (hyperbola-like decay)
1. Concept:

The electrostatic repulsion between two point charges follows an inverse square law regarding their separation distance.

2. Formula:

$$ F = \frac{k q_1 q_2}{x^2} \implies F \propto \frac{1}{x^2} $$

3. Solution:

  • Because the force varies as \( 1/x^2 \), the graph of \( F \) versus \( x \) is not linear.


  • As \( x \) increases, \( F \) decreases rapidly but never truly reaches zero. This forms a steep decaying curve, characteristic of an inverse square relationship.


4. Why other options are incorrect:

A straight line would imply \( F \propto -x \), which is incorrect. A positive slope would imply force increases with distance. The true relationship is non-linear and decaying.

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