✓ Board-verified
Science · 2025 · 2 marks
CBSE 2025 · Region 5 · Set 2 · Q22
(A) Use Ohm's law to determine the potential difference across the 6 Ω resistor in the following circuit when key is closed:
Use Ohm's law to determine the potential difference across the $\displaystyle 6 \Omega$ resistor in the following circuit when key is closed :
Prove that if the current through a resistor is increased by $\displaystyle 100$%, then the increase in power dissipated through the resistor will be $\displaystyle 300$%.
Marking-scheme solution
(A) Total resistance in the circuit
\[\mathrm{R}=\mathrm{R}_{1}+\mathrm{R}_{2}+\mathrm{R}_{3}=12 \Omega
\]
Voltage of the battery = $\displaystyle 6$ V
\[\therefore I=\frac{V}{R}=\frac{6}{12}=0.5 \mathrm{~A}
\]∴ Potential difference across \(\displaystyle 6 \Omega\) resistor \(\displaystyle =0.5 \mathrm{~A} \times 6 \Omega=3.0 \mathrm{~V}\) OR
(B) \(\displaystyle \mathrm{P}_{1}=\mathrm{I}^{2} \mathrm{R} \mathrm{P}_{2}=(2 \mathrm{I})^{2} \mathrm{R}=4 \mathrm{I}^{2} \mathrm{R}[100 \%\) increase in current means current becomes 2I]
∴ Increase in power dissipated \(\displaystyle =\mathrm{P}_{2}-\mathrm{P}_{1}=4 \mathrm{I}^{2} \mathrm{R}-\mathrm{I}^{2} \mathrm{R}=3 \mathrm{I}^{2} \mathrm{R}\)
\[=3 \mathrm{P}_{1}
\]
Percentage increase in power dissipated \(\displaystyle =\frac{3 \mathrm{P}_{1}}{\mathrm{P}_{1}} \times 100=300 \%\)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 2025 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.