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Science · 2024 · 3 marks
CBSE 2024 · Region 5 · Set 3 · Q32
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…
A $\displaystyle 2000$ W heater has a resistance of about $\displaystyle 25 \Omega$, whereas a $\displaystyle 100$ W bulb has a resistance of $\displaystyle 500 \Omega$. When $\displaystyle 220$ V is applied on these, then which of the two
(a)
can carry large currents ?
(b)
may be used with an electrical circuit having $\displaystyle 1$•$\displaystyle 0$ A rating ?
(c)
will be fitted with a $\displaystyle 15$ A electric board and not with a $\displaystyle 5$ A electric board ? Justify your answer in each case.
Marking-scheme solution
(a) $\displaystyle 2000$ W heater , For heater, \(\displaystyle \mathrm{I}_{1}=\frac{P}{V}=9.09 \mathrm{~A}\); For Bulb, \(\displaystyle \mathrm{I}_{2}=\frac{P}{V}=0.45 \mathrm{~A}\)
\[\mathrm{I}_{1}>\mathrm{I}_{2}
\]
(b) $\displaystyle 100$ W bulb
\[\mathrm{I}_{2}=\frac{P}{V}=0.45 \mathrm{~A}
\]
As it draws only $\displaystyle 0$•$\displaystyle 45$ A which is less than $\displaystyle 1$ A.
(c)
$\displaystyle 2000$ W heater
\[\mathrm{I}_{1}=\frac{P}{V}=9.09 \mathrm{~A}
\] As the current drawn is $\displaystyle 9.09$ A which is higher than $\displaystyle 5.0$ A.
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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.