Which of the following statements are correct?
A. Two major types of resistors are wire bound resistors and carbon resistors.
B. Mobility is the drift velocity per unit electric field.
C. The internal resistance of dry cells is much lower than the common electrolytic cells.
D. In electrolytic liquids, electrons carry the electric current.
E. Potentiometer is unaffected by the internal resistance of the source.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → A, B and E Only
(A) Two major types of resistors are wire bound resistors and carbon resistors. — Correct. Commercial resistors are made either by winding an alloy wire (manganin, constantan, nichrome) or from carbon; these are the two major types.
(B) Mobility is the drift velocity per unit electric field. — Correct. Mobility is defined as \( \mu = v_d/E \), the magnitude of the drift velocity per unit electric field.
(C) The internal resistance of dry cells is much lower than the common electrolytic cells. — Incorrect. It is the other way round: the paste inside a dry cell conducts poorly, so the internal resistance of a dry cell is much higher than that of common electrolytic cells.
(D) In electrolytic liquids, electrons carry the electric current. — Incorrect. In an electrolyte the current is carried by positive and negative ions.
(E) Potentiometer is unaffected by the internal resistance of the source. — Correct. At the balance point no current is drawn from the cell being measured, so there is no drop across its internal resistance and the potentiometer reads its emf itself.
Note: Statements (B), (C) and (D) of this question are from the latest textbook (2026-27). Statements (A) and (E), on the two types of resistors and on the potentiometer, are printed only in the pre-rationalised textbook (2022-23). They were removed from the latest book, and they also appear to be out of the CUET 2026 syllabus.
NCERT (2026-27):
Mobility – “… In metals, these mobile charge carriers are electrons; in an ionised gas, they are electrons and positive charged ions; in an electrolyte, these can be both positive and negative ions. An important quantity is the mobility μ defined as the magnitude of the drift velocity per unit electric field:
\( \displaystyle \mu = \frac{|v_d|}{E} \qquad (3.24) \)”
Cells, Emf, Internal Resistance – “… The internal resistance of dry cells, however, is much higher than the common electrolytic cells.”
NCERT (Pre-rationalised edition, 2022-23):
Resistivity of Various Materials – “… Commercially produced resistors for domestic use or in laboratories are of two major types: wire bound resistors and carbon resistors.”
Potentiometer – “… The potentiometer has the advantage that it draws no current from the voltage source being measured. As such it is unaffected by the internal resistance of the source.”