Parallel Circuit Physics Example 3

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Example 3

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A 10 Ω10 \text{ } \Omega and a 15 Ω15 \text{ } \Omega resistor are in parallel. What is the combined resistance?

Solution

  1. 1
    Use the parallel formula: 1RT=110+115=330+230=530\frac{1}{R_T} = \frac{1}{10} + \frac{1}{15} = \frac{3}{30} + \frac{2}{30} = \frac{5}{30}
  2. 2
    RT=305=6 ΩR_T = \frac{30}{5} = 6 \text{ } \Omega

Answer

RT=6 ΩR_T = 6 \text{ } \Omega
The parallel combination is always less than the smallest resistor. The product-over-sum shortcut also works: RT=10×1510+15=15025=6 ΩR_T = \frac{10 \times 15}{10 + 15} = \frac{150}{25} = 6 \text{ } \Omega.

About Parallel Circuit

A parallel circuit connects components in separate branches between two common nodes, so each component gets the full source voltage.

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