Electric Resistance and Simple Circuits | Physics JEE previous year questions with Solutions

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Topic Question Set

Q 11 :
From the combination of resistors with resistance values $R_{1} = R_{2} = R_{3} = 5 Ω$ and $R_{4} = 10 Ω$ , which of the following combination is the best circuit to get an equivalent resistance of $6 Ω$ ? [2025]

1

2

3

4

(1)

$\frac{1}{R_{eq}} = \frac{1}{10} + \frac{1}{15} = \frac{3 + 2}{30} = \frac{1}{6} \Rightarrow R_{e q} = 6 Ω$

Q 12 :
A wire of resistance R is bent into a triangular pyramid as shown in figure with each segment having same length. The resistance between points A and B is $R / n$ . The value of n is: [2025]

16
14
10
12

1

2

3

4

(4)

As, $r = \frac{R}{6}$

(As balanced wheat stone bridge is formed)

Now, Equivalent resistance between A and B can be written as

Clearly, $R_{1} = \frac{r}{6}$

So, $R_{A B} = R_{1} ∥ 2 R_{1} ∥ 2 R_{1}$

$\Rightarrow \frac{1}{R_{A B}} = \frac{1}{R_{1}} + \frac{1}{2 R_{1}} + \frac{1}{2 R_{1}} = \frac{4}{2 R_{1}} = \frac{2}{R_{1}}$

$\Rightarrow R_{A B} = \frac{R_{1}}{2} = \frac{r}{12}$

Q 13 :
A wire of resistance 9 $Ω$ is bent to form an equilateral triangle. Then the equivalent resistance across any two vertices will be ____ ohm. [2025]

0%

(2)

9 $Ω$ is the resistance of whole wire

$∴$ Resistance of each wire = 3 $Ω$

$∴$ Equivalent resistance = 2 $Ω$

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