✓ Board-verified
Science · 2026 · 2 marks
CBSE 2026 · Region 1 · Set 1 · Q34
(a) The resistance of a wire of 0.01 cm radius and 1.0 cm length is 7 Ω. Calculate its resistivity.
(a)
The resistance of a wire of $\displaystyle 0.01$ cm radius and $\displaystyle 1.0$ cm length is $\displaystyle 7 \Omega$. Calculate its resistivity.
OR
(b)
An electric heater is rated $\displaystyle 220$ V; $\displaystyle 11$ A. Calculate the power consumed if the heater is operated at $\displaystyle 200$ V.
Marking-scheme solution
(a)
\(\displaystyle \mathrm{r}=0.01 \mathrm{~cm}=1 \times 10^{-4} \mathrm{~m}\)
\[\begin{aligned}
& l=1 \mathrm{~cm} \\
& \mathrm{R}=\rho \frac{l}{\mathrm{~A}}
\end{aligned}
\]
\[\rho=\frac{\mathrm{RA}}{l}=\frac{R \times \pi r^{2}}{l}
\]
\[\rho=\frac{7 \times 22 \times 10^{-8}}{7 \times 0.01}
\]
\[\rho=22 \times 10^{-8} \times 10^{2}
\]
\[\rho=22 \times 10^{-6} \Omega \mathrm{~m}=2.2 \times 10^{-5} \Omega \mathrm{~m}
\]
(b)
Resistance of electric heater \(\displaystyle \mathrm{R}=\frac{\mathrm{V}}{\mathrm{I}}\)
\[\mathrm{R}=\frac{220}{11}
\]
\[R=20 \Omega
\]
\[P=\frac{V^{2}}{R}
\]
\[\mathrm{P}=\frac{200 \times 200}{20}
\]
\[\text { P = 2000W/ } 2 \text { kW }
\]
More from Electricity
- (i) Consider the following electric circuit: Calculate the values of the following: (I) Total resistance of the circuit. (II) The total electric…2026
- A 2000 W heater has a resistance of about 25 Ω, whereas a 100 W bulb has a resistance of 500 Ω. When 220 V is applied on these, then which of the two…2024
- Show how you would connect three resistors each of resistance 6 Ω, so that the combination has a resistance of 9 Ω. Also justify your answer. OR In…2024
- In domestic electric circuits the wiring with 15 A current rating is for the electric devices which have2023
- Assertion: Electrons move from lower potential to higher potential in a conductor. Reason (R): A dry cell maintains electric potential difference…2024
- (i) State whether the currents and potential difference in all the bulbs will be same or different when in a circuit three bulbs of: same wattage are…2024
- Consider two lamps A and B of rating 50 W; 220 V and 25 W; 220 V respectively. Find the ratio of the resistances of the two lamps (i.e. R_A: R_B ).…2025
- Study the given electric circuit in which 2 A electric current is flowing between points X and Y. (i) Using the battery, key, voltmeter and ammeter…2026
CBSE Class 10 Science past-paper question from the 2026 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.