Read the passage and answer the following questions.
A metal rod held in hand and rubbed with wool will not show any sign of being charged. However, if a metal rod with a wooden or plastic handle is rubbed without touching its metal part, it shows signs of charging. Suppose we connect one end of a copper wire to a neutral pith ball and the other end to a negatively charged plastic rod. We will find that the pith ball acquires a negative charge. If a similar experiment is repeated with a nylon thread or a rubber band, no transfer of charge will take place from the plastic rod to the pith ball.
Consider the following statements:
(A) When some charge is transferred to a conductor, it spreads over the whole surface of the conductor.
(B) In electrolytes, only the negative ions are free to move.
(C) Semiconductors offer a resistance to the movement of charges that lies between that of conductors and insulators.
(D) When a body is charged by rubbing, the electrons transferred form a large part of all the electrons in the body.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → (A) and (C) only
Conductors have charges that are free to move, while insulators hold their charges in place. Semiconductors come in between.
(A) When some charge is transferred to a conductor, it spreads over the whole surface of the conductor. — True. The charges in a conductor are free to move, so the added charge spreads out. On an insulator it stays where it is put.
(B) In electrolytes, only the negative ions are free to move. — False. In electrolytes, both positive and negative ions are mobile. In metals, the mobile charges are electrons.
(C) Semiconductors offer a resistance to the movement of charges that lies between that of conductors and insulators. — True. This in-between resistance is what places semiconductors in a third class.
(D) When a body is charged by rubbing, the electrons transferred form a large part of all the electrons in the body. — False. Only a very small fraction of the electrons of the body is transferred during rubbing.
NCERT (2026-27):
Conductors and Insulators – “When some charge is transferred to a conductor, it readily gets distributed over the entire surface of the conductor.”
Summary – “In metals, the mobile charges are electrons; in electrolytes both positive and negative ions are mobile.”
Conductors and Insulators – “There is a third category called semiconductors, which offer resistance to the movement of charges which is intermediate between the conductors and insulators.”
Electric Charge – “Also the number of electrons, that are transferred, is a very small fraction of the total number of electrons in the material body.”