Which one of the following charge cannot exist on a body? (a) 2e (b) 3e (c) 3.5e (d) -4e

Question of 67

Q. Which one of the following charge cannot exist on a body?

(a)

2\,e

(b)

3\,e

(c)

3.5\,e

(d)

-4\,e

Karnataka PUCKarnataka II PUC Board 2026MCQ· 1mImportance★★★★★

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Concept understanding — Quantization of Charge

Quantization of Charge

Imagine you are at a water fountain. You can fill your bottle with any amount of water — a little, a lot, or anything in between. Water is continuous. Now imagine instead that you are buying marbles. You can only buy marbles in whole numbers: 1 marble, 2 marbles, 15 marbles. You cannot buy half a marble or 2.7 marbles. Electric charge behaves like marbles, not like water.

That is the core intuition: charge comes in discrete packets. You cannot have an arbitrary amount of charge. You can only have whole-number multiples of a smallest possible chunk.

The smallest chunk: the elementary charge

That smallest chunk is called the elementary charge, denoted by the symbol $e$ . Its value is:

e = 1.602 \times 10^{-19} \text{ coulombs}

This is the magnitude of charge carried by a single proton (positive) or a single electron (negative). A proton has charge $+e$ , an electron has charge $-e$ .

Important

Every charged object in the universe — from a rubbed balloon to a lightning bolt — carries a total charge that is an integer multiple of $e$ . No exception has ever been observed among free, isolated charges. (Quarks carry fractional charges of $\pm e/3, \pm 2e/3$ but are always confined inside composite particles such as protons and neutrons, whose own net charge is still an integer multiple of $e$ .)

The precise statement

If $q$ is the total charge on any object, then:

q = n e

where $n$ is an integer ( $n = 0, \pm 1, \pm 2, \pm 3, \dots$ ).

The sign of $n$ tells you whether the charge is positive or negative. The magnitude $|n|$ tells you how many elementary charges are present (in excess or deficit).

q = n e, \quad n \in \mathbb{Z}

Why this matters

This is not a mathematical trick. It is a fundamental law of nature. It means:

You cannot have a charge of $0.5e$ or $1.7e$ .
If you measure the charge on any object, you will always find it to be $0$ , $\pm e$ , $\pm 2e$ , $\pm 3e$ , and so on.
All charge transfer — rubbing, conduction, induction — happens by moving whole electrons or protons. You cannot transfer a fraction of an electron.

Watch out

A common mistake is to think that because charge values like $3.2 \times 10^{-19} \text{ C}$ look like decimals, they are not multiples of $e$ . But $3.2 \times 10^{-19} \text{ C}$ is exactly $2e$ (since $2 \times 1.6 \times 10^{-19} = 3.2 \times 10^{-19}$ ). Always check by dividing by $e$ — the result must be an integer.

A concrete example

A glass rod rubbed with silk acquires a charge of $+4.8 \times 10^{-19} \text{ C}$ . How many electrons were transferred?

Divide the total charge by $e$ :

n = \frac{+4.8 \times 10^{-19}}{1.6 \times 10^{-19}} = +3

So the rod lost exactly 3 electrons. It could not have lost 2.5 or 3.7 electrons. The charge is $+3e$ .

Why this is called "quantization" …

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(c) $3.5\,e$ …

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

Showing the 12 most recent of 27 on this concept.

CBSE 2026Set V11 markMCQ
$Q. Which one of the following charge cannot exist on a body?$
(a) $2\,e$
(b) $3\,e$
(c) $3.5\,e$
(d) $-4\,e$
›Reveal solutionSolution

(c) $3.5\,e$ …

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CBSE 2026Set ANNUAL1 markMCQ
$Q. Number of electrons in one coulomb charge are -$
(i) $6.25\times10^{18}$
(ii) $6.25\times10^{12}$
(iii) $6.25\times10^{10}$
(iv) $6.25\times10^{14}$
›Reveal solutionSolution

1 C of charge contains $1/e$ electrons.

The charge on one electron is $e=1.6\times10^{-19}$ C. The number of electrons whose total charge is 1 coulomb is $n=\dfrac{1}{e}=\dfrac{1}{1.6\times10^{-19}}=6.25\times10^{18}$ .

…

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CBSE 2026Set DS1 markMCQ
$1 \times 10^{-7}$
i) $10^{7}$
ii) $1.6 \times 10^{19}$
iii) $6.25 \times 10^{11}$
iv) $9 \times 10^{12}$
›Reveal solutionSolution

Charge is quantised, so $n = Q/e = 6.25\times10^{11}$ electrons.

Concept. Charge exists only in whole multiples of the electronic charge $e = 1.6\times10^{-19}$ C (quantisation of charge). If a metal piece loses a charge $Q$ , the number of electrons removed is $n = \dfrac{Q}{e}$ .

Calculation. …

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CBSE 2026Set ANNUAL1 markMCQ
$Q. An object has a negative charge of 1 coulomb. The number of excess electrons on it is$
(a) 6.25 x 10^-18
(b) 1.6 x 10^19
(c) 1.6 x 10^-19
(d) 6.25 x 10^18
›Reveal solutionSolution

Charge is quantised: any charge Q is made up of a whole number of electron charges e, so n = Q/e.

A negative charge means the object has more electrons than protons. Each electron carries a charge of magnitude e = 1.6 x 10^-19 C. If the object carries a total (excess) charge of magnitude Q, the number of excess electrons is

…

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CBSE 2025Set 55/4/11 markMCQ
$8.0 \times 10^{-12}$
›Reveal solutionSolution
When a body gains positive charge, it loses electrons; the mass change equals the number of electrons lost times the electron mass. For $8.0 \times 10^{-12}$ C, the body decreases by $4.55 \times 10^{-23}$ kg.

Why charging changes mass

Charging a body means adding or removing electrons. Since electrons have mass ( $m_e = 9.1 \times 10^{-31}$ kg), any change in the number of electrons changes the body's total mass.

The sign of the charge tells us what happened:

Positive charge: electrons were removed → mass decreases

Negative charge: electrons were added → mass increases

The magnitude of charge tells us how many electrons moved, since each electron carries charge $e = 1.6 \times 10^{-19}$ C.

Finding the mass change

Determine the number of electrons involved

The charge acquired is $Q = 8.0 \times 10^{-12}$ C (positive). The number of electrons that must have been removed is:

$n = \frac{Q}{e} = \frac{8.0 \times 10^{-12}}{1.6 \times 10^{-19}}$ $n = 5.0 \times 10^{7} \text{ electrons}$

Calculate the total mass of these electrons

Each electron has mass $m_e = 9.1 \times 10^{-31}$ kg, so the total mass lost is:

$\Delta m = n \times m_e = 5.0 \times 10^{7} \times 9.1 \times 10^{-31}$ $\Delta m = 45.5 \times 10^{-24} = 4.55 \times 10^{-23} \text{ kg}$

Determine the direction of change …
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CBSE 2025Set JS1 mark
$2.4 \times 10^{-18}$
›Reveal solutionSolution

A positive charge of $2.4\times10^{-18}$ C corresponds to a shortage of $n=q/e=15$ electrons.

Concept — quantisation of charge. Charge exists only in integer multiples of the electronic charge $e=1.6\times10^{-19}$ C: $q=ne$ . A positive conductor has lost electrons, so it has a deficit of electrons.

Solution. …

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CBSE 2025Set A1 mark
$Q. Fill in the blank with appropriate word: One coulomb charge has ______ electrons.$
›Reveal solutionSolution

One coulomb of charge corresponds to about 6.25 × 10¹⁸ electrons.

Charge is quantised: total charge $q = ne$ , where $n$ is the number of electrons (or elementary charges) and $e = 1.6\times10^{-19}$ C is the magnitude of charge on a single electron. For $q = 1$ C:

…

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CBSE 2025Set A1 mark
$Q. Write answer in one sentence: Write mathematical form of quantisation of electric charge.$
›Reveal solutionSolution

Quantisation of charge is expressed mathematically as q = ne.

Experiments (starting with Millikan's oil-drop experiment) show that electric charge is never continuous but always occurs in discrete, integral multiples of a smallest indivisible unit of charge, called the elementary charge $e = 1.6\times10^{-19}$ C (the magnitude of the charge on an electron or proton). This is expressed mathematically as:

$q = ne$

…

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CBSE 2025Set ANNUAL1 markMCQ
$Q. How many electrons will have a charge of one Coulomb?$
(a) 6.25 x 10^18
(b) 6.25 x 10^19
(c) 5.25 x 10^18
(d) 5.25 x 10^19
›Reveal solutionSolution

Charge is quantized in units of the electronic charge e = 1.6 x 10^-19 C, so the number of electrons needed to make up 1 C is n = Q/e.

Any charge Q is an integer multiple of the elementary charge: Q = n e.

Here Q = 1 C and e = 1.6 x 10^-19 C, so

n = Q/e = 1 / (1.6 x 10^-19) = 6.25 x 10^18

…

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CBSE 2024Set A1 markMCQ
$Q. Number of electrons present in 8 coulomb negative charge is (A) 5 \times 10^19 (B) 2.5 \times 10^19 (C) 12.8 \times 10^19 (D) 1.6 \times 10^19$
›Reveal solutionSolution

n = Q/e = 8 ÷ (1.6×10⁻¹⁹) = 5×10¹⁹ electrons.

Charge is quantised: total charge $Q = n\,e$ , where $e = 1.6\times10^{-19}$ C.

…

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CBSE 2024Set ANNUAL1 markMCQ
$Q. The minimum amount of charge observed so far is$
(a) 1 C
(b) 4.8 x 10^-13 C
(c) 1.6 x 10^-19 C
(d) 1.6 x 10^19 C
›Reveal solutionSolution

Charge is quantised: every observable free charge is an integer multiple of the elementary charge e = 1.6 x 10^-19 C, the smallest charge ever measured on a free particle.

Millikan's oil-drop experiment established that electric charge does not take arbitrary values but always occurs as an integral multiple of a smallest unit, the electronic charge

$e = 1.6 \times 10^{-19}\ \text{C}$

…

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CBSE 2024Set ANNUAL1 mark
$q_1 + q_2 = 0$
›Reveal solutionSolution

$q_1+q_2=0$ means the two charges are equal in magnitude and opposite in sign, giving zero net charge for the pair — the defining condition of a system like an electric dipole.

If $q_1+q_2=0$ , then $q_2=-q_1$ : the two charges have exactly equal magnitude but opposite polarity (one is $+q$ , the other is $-q$ ). This does not mean there is no electric field around them — a pair of equal and opposite charges separated by some distance still produces a field (this is precisely the definition of an electric dipole, with dipole moment $p=q\times(\text{separation})$ , and it is only the algebraic (net) charge of the pair that vanishes, not the field. It also means that if this pair is enclosed inside a Gaussian …

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Q.Which one of the following charge cannot exist on a body?

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