The Wheatstone bridge shown in the figure below, gets balanced when the carbon resistor used as R 1 has the colour code (orange, red, brown). The resistors R 2 and R 4 are 80 Ω and 40 Ω , respectively

Question

The Wheatstone bridge shown in the figure below, gets balanced when the carbon resistor used as $R_{1}$ has the colour code (orange, red, brown). The resistors $R_{2}$ and $R_{4}$ are $80 Ω$ and $40 Ω$ , respectively. Assuming that the colour code for the carbon resistors gives their accurate values, the colour code for the carbon resistor, used as $R_{3}$ , would be

TestHub · Accepted Answer

Colour band A and B indicate the first two significant figures of resistance in 'ohm', while the C band gives the decimal multiplier i.e., the number of zeros that follows the two significant figures A and B . The last band D indicates the tolerance in percentage about the indicated value or in other word, it represents the percentage accuracy of the indicated value. For R 1 , the given colour of the rings of a carbon resistor are orange, red, brown then, the value of resistance is R 1 = 32 × 10 1 Condition for balance in the Wheat stone's bridge is R 1 R 3 = R 2 R 4 So, 320 R 3 = 80 40 ∴ R 3 = 160 Ω , so colour coding of resistor R 3 is Brown → 1 Blue → 6 Brown → 1 16 × 10 1 ⇒ 160 Ω

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