Which of the following statements are correct?
A. Electrical resistivity of copper is low.
B. Temperature coefficient of resistance for semiconductors is positive.
C. On carbon resistors, colour of the second strip indicates the multiplier.
D. During charging of a cell, the terminal potential difference becomes greater than the emf of the cell.
E. The cells are connected in series to get more voltage, than cells connected in parallel.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → A, D and E only
(A) Electrical resistivity of copper is low — Correct. Copper has a resistivity of about \( 1.7\times10^{-8}\,\Omega\,\mathrm{m} \), which is why it is the usual material for wires.
(B) Temperature coefficient of resistance for semiconductors is positive — Incorrect. For semiconductors the resistivity falls as the temperature rises, because more charge carriers are released, so the temperature coefficient is negative.
(C) On carbon resistors, colour of the second strip indicates the multiplier — Incorrect. The first two strips give the first two digits of the value; the third strip is the multiplier and the fourth is the tolerance.
(D) During charging of a cell, the terminal potential difference becomes greater than the emf of the cell — Correct. While charging, the current enters the cell against its emf, so the external source must also supply the drop across the internal resistance: \( V = \varepsilon + Ir \gt \varepsilon \). On discharge it is \( V = \varepsilon - Ir \).
(E) The cells are connected in series to get more voltage, than cells connected in parallel — Correct. In series the emfs add, \( \varepsilon_{\mathrm{net}} = n\varepsilon \), whereas identical cells in parallel give only the emf of a single cell.
Note: Statements (A), (B) and (E) of this question are from the latest textbook (2026-27). Statement (C), on the colour code of carbon resistors, is printed only in the pre-rationalised textbook (2022-23). It was removed from the latest book, and it also appears to be out of the CUET 2026 syllabus.
NCERT (2026-27):
Resistivity of Various Materials – “… Metals have low resistivities in the range of 10–8 Ωm to 10–6 Ωm.”
Temperature Dependence of Resistivity – “… Unlike metals, the resistivities of semiconductors decrease with increasing temperatures.”
Cells in Series and in Parallel – “… The rule for series combination clearly can be extended to any number of cells: (i) The equivalent emf of a series combination of n cells is just the sum of their individual emf’s, and (ii) The equivalent internal resistance of a series combination of n cells is just the sum of their internal resistances.”
NCERT (Pre-rationalised edition, 2022-23):
Resistivity of Various Materials – “… The first two bands from the end indicate the first two significant figures of the resistance in ohms. The third band indicates the decimal multiplier (as listed in Table 3.2).”