State the three fundamental properties of electric charge -- additivity, conservation, and quantisation -- exp

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Q. State the three fundamental properties of electric charge -- additivity, conservation, and quantisation -- explaining each in one or two sentences with a suitable example.

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✓ Free question

Additivity. If a body carries charges $q_1,q_2,\ldots$ at different points, its total charge is the plain algebraic (scalar) sum $Q=q_1+q_2+\cdots$ , with signs included -- e.g. a body with $+5\ \mu\text{C}$ and $-2\ \mu\text{C}$ has net charge $+3\ \mu\text{C}$ .

Conservation. The total charge of an isolated system never changes. Example: when a plastic rod is rubbed with wool, electrons move from the wool onto the rod; the rod becomes negatively charged and the wool becomes equally positively charged, so the total charge of the rod-wool system remains exactly zero throughout.

Quantisation. Charge is never observed in any amount other than an integral multiple of the elementary charge $e=1.6\times10^{-19}\ \text{C}$ : $q=ne$ , $n=0,\pm1,\pm2,\ldots$ . Example: an electron carries charge $-e$ ; a body that has gained exactly 5 extra electrons carries charge $-5e$ , never, say, $-4.5e$ .

✓Final answer

Q=\sum q_i

Same / Similar Concept — real previous-year questions on the same or a closely similar concept, not this exact question.

CBSE 2026Set ANNUAL1 markMCQ
$Q. When a glass rod is rubbed with a silk cloth the charge acquired by glass rod is$
(a) Positive
(b) Negative
(c) Both positive and negative
(d) None of these
›Reveal solutionSolution

Charging by friction just moves electrons from one material to the other - it never creates charge.

When two different insulating materials are rubbed together, electrons are transferred from the material that holds them less tightly to the one that holds them more tightly. This is a property of the two materials (their position in the triboelectric series), not something created by the rubbing itself - the TOTAL charge of the glass+silk system stays zero (conservation of charge).

For glass rubbed with silk, silk has a stronger pull on electrons than glass does. So electrons move FROM the glass TO the silk. The glass rod, having lost electrons, is left with an excess of protons - a net positive charge. The silk cloth, having gained those electrons, becomes negatively charged by an exactly equal amount.

✓Final answer
$(a) Positive - glass loses electrons to silk on rubbing, leaving the glass rod positively charged.$
CBSE 2022Set ANNUAL1 mark
$Q. A ............ charged particle produced an electric field only around it. (Fill up the blank.) OR Above Curie temperature, a ferromagnetic material is found to behave as a paramagnetic substance. Point out right or wrong.$
›Reveal solutionSolution

A charge at rest produces only a static electric field; a moving charge additionally produces a magnetic field.

A charge produces an electric field around it regardless of its state of motion. However, a magnetic field is produced only by a moving charge (i.e., by a current). So a charged particle that is stationary (at rest) produces an electric field only, with no accompanying magnetic field, since there is no current associated with it.

✓Final answer
$A stationary charged particle produces an electric field only around it.$
CBSE 2020Set ANNUAL1 markMCQ
$Q. A positively charged body has$
(a) excess of electrons
(b) deficit of electrons
(c) excess of protons
(d) deficit of protons
›Reveal solutionSolution
A body's charge changes only through the gain or loss of electrons, never protons, so a positive charge always means a deficit of electrons.

Protons are locked inside the nucleus and cannot be added to or removed from a body by ordinary charging processes (friction, conduction, induction). Only the loose outer electrons can transfer between bodies.

If a body LOSES electrons, its protons now outnumber its electrons, so it carries a net POSITIVE charge - this is a deficit of electrons, not an excess of protons (the proton number is unchanged).

If a body GAINS electrons, it carries a net NEGATIVE charge.

So the correct description of a positively charged body is that it has a deficit of electrons.

✓Final answer
$(b) Deficit of electrons.$

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Q.State the three fundamental properties of electric charge -- additivity, conservation, and quantisation -- explaining each in one or two sentences with a suitable example.

Concept understanding — Electric Charge and Its Properties

Q.State the three fundamental properties of electric charge -- additivity, conservation, and quantisation -- explaining each in one or two sentences with a suitable example.

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