✓ Board-verified
Physics · 2025 · 2 marks
CBSE 2025 · Region 5 · Set 1 · Q21
The resistance of a wire at 25^° C is 10 · 0 Ω. When heated to 125^° C, its resistance becomes 10 · 5 Ω. Find (i) the temperature coefficient of…
The resistance of a wire at $\displaystyle 25^{\circ} \mathrm{C}$ is $\displaystyle 10 \cdot 0 \Omega$. When heated to $\displaystyle 125^{\circ} \mathrm{C}$, its resistance becomes $\displaystyle 10 \cdot 5 \Omega$. Find (i) the temperature coefficient of resistance of the wire, and (ii) the resistance of the wire at $\displaystyle 425^{\circ} \mathrm{C}$.
Marking-scheme solution
(i)
$\displaystyle R_{2}=R_{1}\left(1+\alpha\left(t_{2}-t_{1}\right)\right)$
$\displaystyle 10.5=10(1+\alpha \times 100)$
$\displaystyle \alpha=5 \times 10^{-4} /{ }^{\circ} \mathrm{C}$
(ii)
$\displaystyle R_{425}=R_{25}(1+\alpha(425-25))$
$\displaystyle =10\left(1+5 \times 10^{-4} \times 400\right)$
$\displaystyle =12 \Omega$
All Current Electricity questions2025 question paperNCERT solutions: Current ElectricityPractice Current Electricity →
More from Current Electricity
- A steady current flows through a metallic wire whose area of cross-section increases continuously from one end of the wire to the other. The…2023
- (i) Define mobility of electrons. Give its SI units. (ii) A steady current flows through a wire AB, as shown in the figure. What happens to the…2023
- What is the order of magnitude of drift velocity of electrons in a conductor? Deduce the relation between the current flowing through a conductor and…2026
- 'Current is a scalar quantity, although we represent current with an arrow.' Explain. Derive the balance condition of a Wheatstone Bridge.2026
- The number of electrons flowing through a conductor per second is 3 · 3 × 10^19. The current flowing through the conductor is:2023
- A student sets up the circuit as shown in the figure to find the value of unknown resistance X and records a set of readings of the voltmeter and the…2026
- Define current density and relaxation time. Derive an expression for resistivity of a conductor in terms of number density of charge carriers in the…2023
- A battery of e. m. f. 12 V and internal resistance 0.5 Ω is connected to a 9.5 Ω resistor through a key. The ratio of potential difference between…2025
CBSE Class 12 Physics past-paper question from the 2025 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.