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Two rods are joined end to end, as shown. Both have a cross-sectional area of 0.01 cm². Each is 1 meter long. One rod is of copper with a resistivity of 1.7 × 10–6 ohm-centimeter, the other is of iron with a resistivity of 10–5 ohm-centimeter. How much voltage is required to produce a current of 1 ampere in the rods?
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- 0.117 V
- 0.00145 V
- 0.0145 V
- 1.7 × 10–6 V
Correct Option: A
Copper rod and iron rod are joined in series.
From ohm’s law V = RI
= (1.7 × 10–6 × 10–2 + 10–5 × 10–2) 0.01 × 10–4 volt
= 0.117 volt (∵ I = 1A)
