What is the formula for Coulomb's Law?

Last Updated: 25 Jun 2026

What is the formula for Coulomb's Law? The most useful approach is to identify the physical quantity, phenomenon, law, or device named in the stem and connect it with its standard definition. Here, the relevant answer is “F = kq1q2/r².” A sound solution relies on the governing concept rather than a memorised option letter, because option order may change in another paper. While reading a question, first note whether it asks for a definition, SI unit, formula, direction, cause, effect, or practical use. The distractors in this question—F = kq/r, F = q1q2/r, F = kq1q2r—do not satisfy the exact condition stated. Revise the definition, symbol, SI unit, formula, and one everyday example as a single learning set.

AF = kq/r

BF = kq1q2/r²

CF = q1q2/r

DF = kq1q2r

Correct Answer: F = kq1q2/r²Your Answer: B

Explanation

accepted physical definition, law, relation, or working principle involved. — the scientifically appropriate response is F = kq1q2/r². Option-wise review: F = kq1q2/r² is correct under the condition given in the stem. F = q1q2/r is also incorrect; although it may be a valid physics term, its definition or application is not the one asked here. F = kq1q2r is incorrect because it fails the governing relation or characteristic relevant to this case. Therefore, option B, F = kq1q2/r², is factually and logically consistent with the question. Coulomb's Law: F = kq1q2/r² where k = 9×10⁹ Nm²/C².

Important Notes

Read the complete stem before looking at the options. Identify whether the demand is a definition, unit, formula, direction, cause, effect, image characteristic, or device principle. In this record, the confirmed answer is F = kq1q2/r².
Learn each concept as a five-part card: definition; common symbol; SI unit; principal equation; and one real-life application. This works for mechanics, heat, optics, sound, electricity, magnetism, and modern physics.
Use dimensional consistency as a quick check for formulas. Both sides of a valid physical equation must have the same dimensions. Units can eliminate distractors quickly, although a dimensionally correct option must still satisfy the actual law.
Eliminate F = kq/r, F = q1q2/r, F = kq1q2r here because none fulfils the exact requirement of the stem. The final answer and correct-index field must point to option B.
Exam memory point: connect F = kq1q2/r² directly with the key wording of the question, then verify it once against the relevant definition or formula before marking the answer.k = 1/4πε₀

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FAQ

SSC CGL Physics FAQs

Common questions and clear answers for this topic.

How many physics questions usually appear in the SSC CGL exam?

Physics typically makes up a small portion of the General Science questions, usually focused on concepts rather than numerical problems.

Which physics topics are most important for SSC CGL?

Basic mechanics, heat, sound and light, and electricity and magnetism are the areas that come up most consistently across previous papers.

Do I need to solve numerical problems for SSC CGL physics?

Rarely. Most questions are conceptual and test everyday understanding rather than calculation skills.

Is NCERT physics enough for SSC CGL preparation?

NCERT textbooks from classes 9 and 10 build a strong enough conceptual base for most of what SSC CGL asks.

How can I make physics concepts easier to remember for SSC CGL?

Connecting concepts to everyday observations, like why a thermos keeps tea warm, makes them far easier to recall than memorizing definitions.

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