JEE MAIN - Physics (2017 - 9th April Morning Slot - No. 22)

The figure shows three circuits I, II and III which are connected to a 3V battery. If the powers dissipated by the configurations I, II and III are P1 , P2 and P3 respectively, then :

JEE Main 2017 (Online) 9th April Morning Slot Physics - Current Electricity Question 280 English
P1 > P2 > P3
P1 > P3 > P2
P2 > P1 > P3
P3 > P2 > P1

Explanation

We have the following cases :

$$\bullet$$ For configuration (I) : Considering as Wheatstone's bridge, we get the equivalent resistance as $${({R_I})_{eq}} = 1\,\Omega $$.

JEE Main 2017 (Online) 9th April Morning Slot Physics - Current Electricity Question 280 English Explanation 1

$$\bullet$$ For configuration (II) : The given configuration is further reduced as follows:

JEE Main 2017 (Online) 9th April Morning Slot Physics - Current Electricity Question 280 English Explanation 2

That is, $${({R_{II}})_{eq}} = {1 \over 2}\,\Omega $$.

$$\bullet$$ For configuration (III) : Similarly, we get $${({R_{III}})_{eq}} = 2\,\Omega $$.

The power is given by

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

Since V is the same for all three configurations, we have the power as a quantity indirectly proportional to the resistance :

$$P \propto {1 \over R}$$

From the above three case, we have $${({R_I})_{eq}} = 1\,\Omega ;\,{({R_{II}})_{eq}} = {1 \over 2}\,\Omega ;\,{({R_{III}})_{eq}} = 2\,\Omega $$, which implies that

$${R_{II}} > {R_I} > {R_{III}}$$

Therefore, $${P_2} > {P_2} > {P_3}$$

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