alleryStart learning →Two point charges q1 and q2 exert a force F on each other. If the value of q1 is doubled while q2 and the separation r stay fixed, what happens to the force F?
AF is cut by half
BF doubles in size
CF stays unchanged
DF quadruples in size
Answer & Solution
Correct answer: B. F doubles in size
1. Coulomb's law states that F is proportional to the product q1 q2, not to either charge squared.
2. Doubling q1 while holding q2 and r fixed doubles the product q1 q2.
3. Since F is directly proportional to that product, F also doubles.
4. Quadrupling only happens if the distance is halved, since distance enters as an inverse square
so option D mixes up the charge and distance dependence, which is the trap to watch for when scaling Coulomb's law.
_Source: OpenStax Physics (CC BY 4.0), Ch 18 "Static Electricity", section 18.2 Coulomb's law_
Keep practising Static Electricity
Browse all Static Electricity questions for HSC (New South Wales), or explore more Physics topics.
Related questions
If the plate area of a parallel-plate capacitor is doubled while the plate separation stayIf the distance between the plates of a capacitor is doubled while the plate area and everA camera flash capacitor of 200 microfarads is charged to a potential difference of 100 V.A capacitor of 10 microfarads is charged to 12 V. Using U_E = (1/2) C V^2, how much energyA 10 microfarad capacitor is to store 120 microcoulombs of charge. Using V = Q/C, what volA capacitor with capacitance 8.9 x 10^-9 F has a voltage of 3.00 x 10^3 V applied across iWhat is the electric potential 1.0 m from a point charge of Q = -25 nC?What are the SI units of the electric field?