Series and Parallel Combinations

Question 1

how should you tackle a problem involving a combination of resistors in series and parallel

Answer 1

• by combining the resistance of the resistors on parallel to find the equivalent single resistance
• then adding it to the resistance in series

Question 2

you have two resistors in parallel with a resistance of 20 and 30 ohms. in series is a resistor with 10 ohms. how would you firstly calculate the total resistance of the resistors in parallel

Answer 2

• using 1 / R = 1 / R1 + 1 / R2
• 1 / R = 1 / 20 + 1 / 30
• 1 / R = 1 / 12
• meaning the total resistance in parallel is 12

Question 3

what are the two ways you can come up with your answer at the end

Answer 3

• you can either just look at 1 / R = 1 / 12 and determine that R has to be 12
• or you can divide 1 / 12 by 1 (1 / (1/12)) to get 12

Question 4

what is your total resistance in the circuit

Answer 4

12 + 10 = 22 ohms