Series/parallel calculations

Instructions:

Following are information and questions on series/parallel circuits.

For the multi-choice questions:

  • choose the correct answer
  • write down your answer.

For the calculation questions:

  • calculate the unknown value
  • choose the appropriate unit
  • write down your answer.

Note:

  • You can print this document and write your answers onto it.
  • You can use a calculator.

Series/parallel circuit diagram

This following circuit diagram contains resistors in series and in parallel.

Circuit diagram showing resistors in series and in parallel

Solving problems in series/parallel circuits requires:

  • calculating value of resistors in series
  • calculating value of resistors in parallel
  • applying Ohm's law to the total circuit
  • applying Ohm's law to an individual area of the circuit
  • using Kirchoff's voltage law for series circuits
  • using Kirchoff's current law for parallel circuits.

Do you know the correct formula to use for each of the above?

Question 1

Which of the following statements reflects Kirchoff's current law ?

  1. Current leaving the supply is less than returning current.
  2. Current leaving the supply is greater than returning current.
  3. Current leaving the supply equals returning current.

 

Current flow into a parallel branch, splits relative to the value of each resistor, then rejoins as it leaves the branch. An example of this is shown in the following diagram.

Circuit diagram showing current flow through resistors in parallel

Question 2

In the following circuit diagram, what is the resistance value of R2?

Circuit diagram showing resistors in parallel

For the next four questions try calculating the unknown values shown in this series/parallel circuit diagram.

Circuit diagram showing resistors in series and in parallel

Question 3

What is the resistance value of the parallel branch?

Question 4

What is the total circuit resistance?

Question 5

What is the voltage across R1?

Question 7

What is the current flow through R4?

Summary

Solving mathematical problems in series/parallel circuits requires:

  • knowledge of Ohm's and kirchoff's laws.

When working on difficult problems involving many resistors, it may:

  • require a number of prior calculations to obtain the values needed to solve the problem
  • be of assistance to redraw the simplified version of the circuit as values are determined.

When you have finished:

  • show your answers to your trainer
  • close this window and choose a new activity from the menu.