The resistance across R and Q in the figure is

Options

A. r/3
B. r/2
C. 2r
D. 6r

Answer

A

Explanation

Two resistances of each side of triangle are connected in parallel. Therefore, the effective resistance of each arm of the triangle would be `(r xx r)/(r + r)= r//2`.
The two arm AB and AC are in series and they together are in parallel with third one.
`therefore " " R'=(r//2)+(r//2)=r`
Total resistance `(1)/(R )=(1)/(r )+(2)/(r )=(3)/(r )rArr R = r//3`.