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Asked by amaarisa | 13th Jul, 2021, 09:36: AM

Expert Answer:

(i) Total current 0.4 A in the circuit flows through 2 Ω resistor and resistor of unknown resistance x Ω
 
(ii) Three resistors 12 Ω , 6 Ω and 3 Ω are in parallel . Hence circuit current 0.4 A is getting divided in these three resitors.
      Hence currents passing through 12 Ω , 6 Ω and 3 Ω are less than 0.4 A
 
Equivalent resistance Req of parallel combination of 12 Ω , 6 Ω and 3 Ω resistors is calculated as follows
 
Req = ( 12 × 6 × 3 ) / [ ( 12 × 6 ) + ( 6 × 3 ) + ( 3 × 12 ) ]  =  (12/7) Ω
 
Current in the circuit = Voltage / Resistance = 6 / [ 2 + (12/7) + x ] = 0.4 = 2/5
 
From above expression we get , x = 79/7 Ω  ≈ 11.7 Ω

Answered by Thiyagarajan K | 13th Jul, 2021, 12:30: PM