SATHEE: Current Electricity 3 Question 5

Current Electricity 3 Question 5

5. Two equal resistances when connected in series to a battery consume electric power of $60 W$ . If these resistances are now connected in parallel combination to the same battery, the electric power consumed will be

(2019 Main, 11 Jan I)

(a) $60 W$

(b) $30 W$

(d) $120 W$

Show Answer

Solution:

Let $P_{1}$ and $P_{2}$ be the individual electric powers of the two resistances, respectively.

In series combination, power is

$P_{0} = \frac{P_{1} P_{2}}{P_{1} + P_{2}} = 60 W$

Since, the resistances are equal and the current through each resistor in series combination is also same. Then,

$P_{1} = P_{2} = 120 W$

In parallel combination, power is

$P = P_{1} + P_{2} = 120 + 120 = 240 W$

Alternate method

Let $R$ be the resistance.

$∴$ Net resistance in series $= R + R = 2 R$

$\begin{aligned} P & = \frac{V^{2}}{2 R} = 60 W \\ \Rightarrow \frac{V^{2}}{R} & = 120 W \end{aligned}$

New resistance in parallel $= \frac{R \times R}{R + R} = R / 2$

$P^{'} = \frac{V^{2}}{R / 2} = 2 \frac{V^{2}}{R} = 240 W$

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Current Electricity 3 Question 5

5. Two equal resistances when connected in series to a battery consume electric power of $60 W$ . If these resistances are now connected in parallel combination to the same battery, the electric power consumed will be

Solution:

Alternate method

इंजीनियरिंग की तैयारी

चिकित्सा तैयारी

एनसीईआरटी पुस्तकें और समाधान

महत्वपूर्ण संसाधन

अन्य संसाधन

पाठ्यक्रम

परीक्षा मंच

नमूना मॉक टेस्ट

सदस्यता

एनसीईआरटी व्यायाम वीडियो समाधान

Current Electricity 3 Question 5

5. Two equal resistances when connected in series to a battery consume electric power of 60W. If these resistances are now connected in parallel combination to the same battery, the electric power consumed will be

Solution:

Alternate method

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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5. Two equal resistances when connected in series to a battery consume electric power of $60 W$ . If these resistances are now connected in parallel combination to the same battery, the electric power consumed will be