SATHEE: Current Electricity 3 Question 4

Current Electricity 3 Question 4

4. Two electric bulbs rated at $25 W, 220 V$ and $100 W, 220 V$ are connected in series across a $220 V$ voltage source. If the $25 W$ and $100 W$ bulbs draw powers $P_{1}$ and $P_{2}$ respectively, then

(2019 Main, 12 Jan I)

(a) $P_{1} = 16 W, P_{2} = 4 W$

(b) $P_{1} = 4 W, P_{2} = 16 W$

(d) $P_{1} = 16 W, P_{2} = 9 W$

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Solution:

Resistance of a bulb of power $P$ and with a voltage source $V$ is given by

$R = \frac{V^{2}}{P}$

Resistance of the given two bulbs are

and

$\begin{aligned} R_{1} = \frac{V^{2}}{P_{1}} = \frac{(220)^{2}}{25} \\ R_{2} = \frac{V^{2}}{P_{2}} = \frac{(220)^{2}}{100} \end{aligned}$

Since, bulbs are connected in series. This means same amount of current flows through them.

$∴$ Current in circuit is

$i = \frac{V}{R_{total}} = \frac{220}{\frac{(220)^{2}}{25} + \frac{(220)^{2}}{100}} = \frac{1}{11} A$

Power drawn by bulbs are respectively,

$\begin{aligned} P_{1} = i^{2} R_{1} = {\frac{1}{11}}^{2} \times \frac{220 \times 220}{25} = 16 W \\ and P_{2} = i^{2} R_{2} = {\frac{1}{11}}^{2} \times \frac{220 \times 220}{100} = 4 W \end{aligned}$

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Current Electricity 3 Question 4

4. Two electric bulbs rated at $25 W, 220 V$ and $100 W, 220 V$ are connected in series across a $220 V$ voltage source. If the $25 W$ and $100 W$ bulbs draw powers $P_{1}$ and $P_{2}$ respectively, then

Solution:

इंजीनियरिंग की तैयारी

चिकित्सा तैयारी

एनसीईआरटी पुस्तकें और समाधान

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नमूना मॉक टेस्ट

सदस्यता

एनसीईआरटी व्यायाम वीडियो समाधान

Current Electricity 3 Question 4

4. Two electric bulbs rated at 25W,220V and 100W,220V are connected in series across a 220V voltage source. If the 25W and 100W bulbs draw powers P1 and P2 respectively, then

Solution:

इंजीनियरिंग की तैयारी

चिकित्सा तैयारी

एनसीईआरटी पुस्तकें और समाधान

महत्वपूर्ण संसाधन

अन्य संसाधन

पाठ्यक्रम

परीक्षा मंच

नमूना मॉक टेस्ट

सदस्यता

एनसीईआरटी व्यायाम वीडियो समाधान

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4. Two electric bulbs rated at $25 W, 220 V$ and $100 W, 220 V$ are connected in series across a $220 V$ voltage source. If the $25 W$ and $100 W$ bulbs draw powers $P_{1}$ and $P_{2}$ respectively, then