Current Electricity Charging Discharging Of Capacitors Question 158

Question: The effective resistance between points P and Q of the electrical circuit shown in the figure is

[IIT-JEE (Screening) 2002]

Options:

A) $ 2Rr/(R+r) $

B) $ 8R,(R+r)/(3R+r) $

C) $ 2r+4R $

D) $ 5R/2+,2r $

Show Answer

Answer:

Correct Answer: A

Solution:

In a circuit, any circuit element placed between points at the same potential can be removed, without affecting the rest of the circuit. Here, by symmetry, points A, B and C are at same potential, for any potential difference between P and Q. The circuit can

Therefore be reduced as shown below Effective resistance $ R _{eq}=\frac{2Rr}{R+r} $ .