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.
Consider the following statements about electric charge:
(A) Charge has magnitude but no direction, like mass.
(B) In an isolated system, particles that carry charge can never be created or destroyed.
(C) A neutral body contains charges, but its positive and negative charges balance each other.
(D) Mass also obeys a law of quantisation, just like charge.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → (A) and (C) only
Charge is a scalar quantity. Its total in an isolated system stays fixed, and it comes only in whole-number multiples of e.
(A) Charge has magnitude but no direction, like mass. — True. Charges add like ordinary numbers, with their signs. So charge is a scalar.
(B) In an isolated system, particles that carry charge can never be created or destroyed. — False. Charged particles can be created or destroyed. Only the net charge stays the same. A neutron can turn into a proton and an electron, with total charge zero before and after.
(C) A neutral body contains charges, but its positive and negative charges balance each other. — True. A neutral body is not free of charge. It has equal amounts of positive and negative charge, so their effects cancel.
(D) Mass also obeys a law of quantisation, just like charge. — False. Quantisation is a law for charge only. There is no such law for mass.
NCERT (2026-27):
Additivity of charges – “Charge has magnitude but no direction, similar to mass.”
Charge is conserved – “It is not possible to create or destroy net charge carried by any isolated system although the charge carrying particles may be created or destroyed … in a process.”
Electric Charge – “Although normally the materials are electrically neutral, they do contain charges; but their charges are exactly balanced.”
Points to Ponder – “8. Quantisation of electric charge is a basic (unexplained) law of nature; … there is no analogous law on quantisation of mass.”