Question

The equivalent resistance between the parts X and Y in the adjoining circuit will be

(A) 2R/3
(B)r
(C) 4r/3
(D) 3r​

Answer 1

Answer:

D

Formula for equivalent resistance in series

R=R

1

+R

2

Formula for equivalent resistance in parallel

R

1

=

R

1

1

+

R

2

1

Now, given circuit can be rearrange as in figure 2

Using formula for equivalent resistance in parallel

R

1

=

R

1

1

+

R

2

1

Equivalent resistance beween B and C =

2

R

and it is in series with resistance(AC), So resistance of lower branch =

2

3R

Now, equivalent resistance between A and B

R

eq

1

=

R

1

+

3R

2

⇒R

eq

=

5

3R

Therefore, D is correct option.