The series combination of three 20 Ω resistances is connected in parallel combination to a 30 Ω resistance. Determine the equivalent resistance of the final combination.
WBBSE
Class X
Physical Science
Current Electricity
03 Mark
2025
Three resistors of 20 Ω each are connected in series.
Resistance in series = 20 + 20 + 20 = 60 Ω
This 60 Ω combination is connected in parallel with a 30 Ω resistor.
Equivalent resistance = \frac{R_1 \times R_2}{R_1 + R_2}
= \frac{60 \times 30}{60 + 30}
= \frac{1800}{90}
= 20 Ω
Hence, the equivalent resistance of the final combination is 20 Ω.
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