# Resistors in series and parallel; power

### Explanation of question 6

If the circuit in Fig. 3.1 is connected across a 40V supply, the p.d. across the 10 resistor will be

1. 28V, the same as the p.d. across the 15 resistor
2. 28V, but different from the p.d. across the 15 resistor
3. 12V, but different from the p.d. across the 15 resistor d 12V, the same as the p.d. across the 15 resistor
4. 12V, the same as the p.d. across the 15 resistor

The answer is :- 4

Total resistance = 20

Total current = total p.d. / total resistance = 40 / 20 = 2 A

P.D. across 14 resistor = 2 x 14 = 28 V,

so p.d. across the parallel combination = 40 - 28 = 12 V,

i.e. the p.d. acrross both the 10 and 15 resistors.

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