Question

class 12 physics
with explanation please​

Answer 1

Answer:

70Ω

Explanation:

the potential difference between PQ is potential difference across the battery

Let the emf of battery be E

potential difference between PQ = E

potential difference per unit length of wire = E/L=E/(100 cm) =λ

Let current passing through 30 Ω and S is i

now potential difference between PR = potential difference across the 30Ω = 30*i

and   potential difference between RS = potential difference across the S = S*i

potential difference between PR = λ*(length of PR in cm ) = (E/100)* (30) = 3E/10 = 30*i

E=100*i

 potential difference between RS = λ*(length of RS in cm ) =  (E/100)* (70) = 7E/10 = Si

substitute E=100i

70*i = S*i

S=70 Ω

HOPE IT IS HELPFUL