JEE Main · 2025 · 07 Apr 2025 · Shift 1 · Current Electricity

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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:

(A)16
(B)14
(C)10
(D)12✓ Correct

Answer: (D)

Solution

The wire forms a regular tetrahedron of six equal edges, so each edge has resistance

r = \frac{R}{6}

. With

A

and

B

taken as two vertices, the symmetry makes the other two vertices an equipotential pair, and the network reduces so that the resistance between any two vertices is

R_{A B} = \frac{r}{2} = \frac{R}{12} .

Comparing with

R_{A B} = \frac{R}{n}

gives

n = 12

JEE Main · 2025 · 07 Apr 2025 · Shift 1 · Single correct option

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