CBSE 2025 · Region 1 · Set 3 · Q22 · 2 marks
Consider two lamps A and B of rating $\displaystyle 50$ W; $\displaystyle 220$ V and $\displaystyle 25 \mathrm{~W} ; 220 \mathrm{~V}$ respectively. Find the ratio of the resistances of the two lamps (i.e. $\displaystyle \mathrm{R}_{\mathrm{A}}: \mathrm{R}_{\mathrm{B}}$ ).Heat produced per second due to a current in a resistor of $\displaystyle 4 \Omega$ is $\displaystyle 400$ joules. Calculate the potential difference across the resistor.
Consider two lamps A and B of rating $\displaystyle 50$ W; $\displaystyle 220$ V and $\displaystyle 25 \mathrm{~W} ; 220 \mathrm{~V}$ respectively. Find the ratio of the resistances of the two lamps (i.e. $\displaystyle \mathrm{R}_{\mathrm{A}}: \mathrm{R}_{\mathrm{B}}$ ).
Heat produced per second due to a current in a resistor of $\displaystyle 4 \Omega$ is $\displaystyle 400$ joules. Calculate the potential difference across the resistor.
Marking-scheme solution
\(\displaystyle \mathrm{P}=\frac{V^{2}}{R}\)
\[\begin{aligned}
\mathrm{R} & =\frac{V^{2}}{P} \\
R_{A} & =\frac{(220)^{2}}{50} \\
R_{B} & =\frac{(220)^{2}}{25} \\
\frac{R_{A}}{R_{B}} & =\frac{1}{2}
\end{aligned}
\]
/
\(\displaystyle \mathrm{P}=\frac{V^{2}}{R}\)
Since V is same means P is inversely proportional to R.
Power of lamp A is double that of B hence Resistance of A is half that of B.
\[\frac{R_{A}}{R_{B}}=\frac{1}{2}
\]
\[\begin{aligned}
& \mathrm{H}=\frac{V^{2}}{R} \times t \\
& 400=\frac{V^{2}}{4} \times 1 \\
& V^{2}=1600 \\
& \mathrm{~V}=40 \mathrm{~V}
\end{aligned}
\]
ElectricityHeating Effect of Electric CurrentApplyvery_short_answermedium
More from Electricity
- Four identical resistors of 12 Ω each are connected in series to form a square ABCD as shown in the figure.…2025 · asked 3×
- The resistance of a wire of 0.01 cm radius is 7 ohms. If the resistivity of the material of the wire is 44 ×…2025 · asked 3×
- The minimum number of identical bulbs of rating 4V; 6W, that can work safely with desired brightness, when…2025 · asked 3×
- Study the circuit shown in which two resistors X and Y of resistances 3 Ω and 6 Ω respectively are joined in…2025 · asked 3×
- Explain the statement "Potential difference between two points is 1 volt". What do the symbols given below…2025 · asked 3×
- A piece of wire of resistance 'R' is cut lengthwise into three identical parts. These parts are then…2025 · asked 3×
- Consider the following electric circuit: Calculate the values of the following: The total resistance of the…2025 · asked 3×
- As shown in the diagram, an electric circuit consisting of an ammeter, a voltmeter, 4 cells of 1 · 5 V each,…2025 · asked 3×
CBSE Class 10 Science past-paper question from the 2025board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.