Read the following passage and answer the questions.
A student studies the charges on four very tiny plastic beads, P, Q, R and S. All four beads are neutral at the start. She charges each bead by rubbing it with a different material. A sensitive meter then gives the charge on each bead. Her readings are: P, \(+8.0\times10^{-19}\ \mathrm{C}\); Q, \(-4.8\times10^{-19}\ \mathrm{C}\); R, \(+3.2\times10^{-19}\ \mathrm{C}\); and S, \(-1.6\times10^{-19}\ \mathrm{C}\).
Next, she puts all four beads in a small closed box. The beads can touch one another inside the box, but no charge can enter or leave it. She also compares each reading with the magnitude of the charge on an electron, \(1.6\times10^{-19}\ \mathrm{C}\). Her teacher tells her that charged bodies in everyday experiments carry much larger charges, of a few microcoulombs.
Match List-I with List-II.
| List-I (Bead) | List-II (Change in its electrons) |
|---|---|
| (A) Bead P | (I) Gained 1 electron |
| (B) Bead Q | (II) Lost 2 electrons |
| (C) Bead R | (III) Gained 3 electrons |
| (D) Bead S | (IV) Lost 5 electrons |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → (A)-(IV), (B)-(III), (C)-(II), (D)-(I)
A positive bead has lost electrons and a negative bead has gained them. The number of electrons is the charge divided by \( e=1.6\times10^{-19}\ \mathrm{C} \).
(A) Bead P — This matches (IV) Lost 5 electrons. Its charge is positive, and \( 8.0\times10^{-19}\ \mathrm{C} \) is 5 times \( e \).
(B) Bead Q — This matches (III) Gained 3 electrons. Its charge is negative, and \( 4.8\times10^{-19}\ \mathrm{C} \) is 3 times \( e \).
(C) Bead R — This matches (II) Lost 2 electrons. Its charge is positive, and \( 3.2\times10^{-19}\ \mathrm{C} \) is 2 times \( e \).
(D) Bead S — This matches (I) Gained 1 electron. Its charge is negative and equal in size to \( e \).
NCERT (2026-27):
Electric Charge – “A body can thus be charged positively by losing some of its electrons. Similarly, a body can be charged negatively by gaining electrons.”
Quantisation of charge – “Experimentally it is established that all free charges are integral multiples of a basic unit of charge denoted by e.”