The document discusses calculating the equivalent resistance of parallel resistors using the formula 1/RT = 1/R1 + 1/R2 + 1/R3 +....1/Rn. It provides an example of calculating the equivalent resistance of three parallel resistors rated at 20 ohms, 50 ohms, and 40 ohms. The equivalent resistance is calculated to be 10.52 ohms.

1. Parallel resistors:

2. Parallel resistors: We use the Formulae 1 / RT = 1 / R1 + 1 / R2 + 1 / R3 + …… 1 / Rn

3. Example: 20 Ω 50 Ω 40 Ω

4. Example: 20 Ω 50 Ω 40 Ω 1/RT = 1/R1 + 1/R2 + 1/R3 + ……1/Rn

5. Example: 20 Ω 50 Ω 40 Ω 1/RT = 1/R1 + 1/R2 + 1/R3 + ……1/Rn 1/RT = 1/ 20 Ω + 1/ 50Ω + 1/ 40Ω

6. Example: 20 Ω 50 Ω 40 Ω 1/RT = 1/R1 + 1/R2 + 1/R3 + ……1/Rn 1/RT = 1/20 Ω + 1/50Ω + 1/40Ω On calculator use to enter fractions a b / c

7. Example: 20 Ω 50 Ω 40 Ω 1/RT = 1/R1 + 1/R2 + 1/R3 + ……1/Rn 1/RT = 1/20 Ω + 1/50Ω + 1/40Ω On calculator use to enter fractions ie: 1 20 1 50 1 40 a b / c a b / c = a b / c a b / c + +

8. Example: 20 Ω 50 Ω 40 Ω 1/RT = 1/R1 + 1/R2 + 1/R3 + ……1/Rn 1/RT = 1/20 Ω + 1/50Ω + 1/40Ω On calculator use to enter fractions ie: 1 20 1 50 1 40 1/RT = 19/200 a b / c a b / c = a b / c a b / c + +

9. Example: 20 Ω 50 Ω 40 Ω 1/RT = 19/200 =+

10. Example: 20 Ω 50 Ω 40 Ω 1/RT = 19/200 To change back to decimal; =+ a b / c

11. Example: 20 Ω 50 Ω 40 Ω 1/RT = 19/200 To change back to decimal; 1/RT = 0.095 a b / c

12. Example: 20 Ω 50 Ω 40 Ω 1/RT = 19/200 To change back to decimal; 1/RT = 0.095 To get inverse =+ a b / c X -1

13. Example: 20 Ω 50 Ω 40 Ω 1/RT = 19/200 To change back to decimal; 1/RT = 0.095 To get inverse RT = 10.52 Ω =+ a b / c X -1

14. Example: 20 Ω 50 Ω 40 Ω 1/RT = 19/200 To change back to decimal; 1/RT = 0.095 To get inverse RT = 10.52 Ω Note your answer should always be smaller than the smallest resistor =+ a b / c X -1