Question

please answer for this question friends​

Answer 1

Option :

$\star \boxed{ \blue{ \bold{3) \: R \: }}}$

•It is a balanced Wheatstone bridge .

• So , no current pass through the CD .

• Upper two resistor becomes in series And lower two also .

• Then both are in parallel combination

Solution refer to the attachment

Answer 2

Answer:

Given:

A circuit has been given.

To find:

The equivalent resistance of the circuit.

Trick :

Pull the terminal A to the other side. You will be able to understand that its a square shaped resistance combination.

Diagram:

Please refer to the attached photo to understand better

Calculation:

We can clearly see that it's a balanced Wheatstone Bridge because of the following reason :

$\frac{r1}{r2} = \frac{r3}{r4}$

So, no current will pass through the middle R resistor.

Now apply parallel and series combinations to get the equivalent resistance.

The upper 2 resistors are in series , hence R + R =2R

The lower 2 resistors are in series hence R + R = 2R

Now these are in Parallel combination.

1/R eq. = 1/2R + 1/2R

=> 1/R eq. = 2/2R

=> 1/R eq. = 1/R

=> R eq. = R

So the equivalent resistance is R