alleryStart learning →In a single loop an 18 V supply has 1 V across its internal resistance and 12 V across one load resistor. What is the drop across the second load resistor?
A18 V
B6 V
C31 V
D5 V
Answer & Solution
Correct answer: D. 5 V
1. Round a closed loop the emf is used up entirely by the drops it drives.
2. So 18 V = 1 V + 12 V + the unknown drop.
3. The accounted drops come to 1 V + 12 V = 13 V.
4. The second load resistor therefore takes 18 V minus 13 V = 5 V.
5. Picking 6 V forgets the 1 V lost inside the supply, which is the drop most often overlooked.
_Source: OpenStax College Physics (CC BY 4.0), Ch 21 "Circuits and DC Instruments", section 21.3 Kirchhoff's Rules_
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