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Science · 2022 · 3 marks
CBSE 2022 · Region 1 · Set 1 · Q12
(a) (i) Define Electric Power and write its SI unit. 1/2+1/2 (ii) Two bulbs rated 100 W; 220 V and 60 W; 220 V are connected in parallel to an…
(i)
Define Electric Power and write its SI unit. $\displaystyle \frac{1}{2}+\frac{1}{2}$
(ii)
Two bulbs rated $\displaystyle 100$ W; $\displaystyle 220$ V and $\displaystyle 60$ W; $\displaystyle 220$ V are connected in parallel to an electric mains of $\displaystyle 220$ V. Find the current drawn by the bulbs from the mains.
(i)
State Joule's law of heating. Express it mathematically when an appliance of resistance R is connected to a source of voltage V and the current I flows through the appliance for a time t.
(ii)
A $\displaystyle 5 \Omega$ resistor is connected across a battery of $\displaystyle 6$ volts. Calculate the energy that dissipates as heat in $\displaystyle 10$ s.
Marking-scheme solution
(a) (i) The rate at which electric energy is dissipated or consumed in an electric circuit.
S.I. unit-watt / V. A / joule per second
(ii)
Current drawn by first bulb
\[I_{1}=\frac{100 \mathrm{~W}}{220 \mathrm{~V}}=\frac{100}{220} \text { ampere }
\]Current drawn by second bulb
Both the bulbs are in parallel
Total current, \(\displaystyle I=I_{1}+I_{2}\)
\[=\left(\frac{100}{220}+\frac{60}{220}\right) \text { ampere }=\frac{160}{220} \mathrm{~A}=0.73 \mathrm{~A}
\]More from Electricity
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CBSE Class 10 Science past-paper question from the 2022 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.