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Science · 2024 · 5 marks
CBSE 2024 · Region 1 · Set 3 · Q34
(A) (i) State whether the currents and potential difference in all the bulbs will be same or different when in a circuit three bulbs of: (a) same…
(i)
State whether the currents and potential difference in all the bulbs will be same or different when in a circuit three bulbs of :
(a)
same wattage are connected in series.
(b)
same wattage are connected in parallel.
(c)
different wattage are connected in series.
(d)
different wattage are connected in parallel.
(ii)
Two identical resistors of $\displaystyle 24 \Omega$ each are connected to a battery of $\displaystyle 6$ V. Calculate the ratio of the power consumed by the resulting combinations with (a) minimum resistance and
(b)
maximum resistance.
Draw a schematic diagram of a circuit consisting of a battery of six 2V cells, a $\displaystyle 6 \Omega$ resistor, a $\displaystyle 12 \Omega$ resistor and a $\displaystyle 18 \Omega$ resistor and a plug key all connected in series. Calculate the following (when key is closed) :
(i)
Electric current flowing in the circuit.
(ii)
Potential difference across $\displaystyle 18 \Omega$ resistor.
(iii)
Electric power consumed in $\displaystyle 18 \Omega$ resistor.
Marking-scheme solution
(A) (i)(a) same current and same potential difference.
(b) same current and same potential difference
(c) same current but different potential difference
(d) different current but same potential difference.
(ii) (a)Minimum resistance - When resistors are in parallel
\[\frac{1}{R}=\frac{1}{24}+\frac{1}{24}
\]
\[\therefore R_{P}=12 \Omega
\]
Power consumed \(\displaystyle P_{1}=\frac{V^{2}}{R_{P}}\)
\[\begin{gathered}
=\frac{6 \mathrm{~V} \times 6 \mathrm{~V}}{12 \Omega} \\
=3 \mathrm{~W}
\end{gathered}
\]
(b)
\[\therefore R_{s}=24 \Omega+24 \Omega=48 \Omega
\]
Power consumed \(\displaystyle P_{2}=\frac{V^{2}}{R_{s}}\)
\[\begin{aligned}
& =\frac{6 V \times 6 V}{48 \Omega} \\
& =\frac{3}{4} W
\end{aligned}
\]
(iii)
Ethene
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CBSE Class 10 Science past-paper question from the 2024 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.