# Electric circuits: Resistors in series and parallel

Introduction

In the past lessons we covered electric circuit diagrams and also measuring current, voltage and resistance. Now we'll be using all that information to do calculations on electric circuits. There's are different ways to connect resistor:

1. Series

2. Parallel

3. Combination of series and parallel

This lesson will be on series and parallel connections.

Watch the video below to understand the differences between resistors in series and resistors in parallel:

At the end of the quest, the learner should be able to:

1. Calculate the equivalent resistance of resistors in series and resistors in parallel.

2. Calculate the current flowing through resistors.

3. Calculate the voltage across resistors.

Answer both question 1 and question 2

Question 1

An electric circuit has the following: A 12V battery, a switch, an ammeter and three resistors in series (2, 4 and 6 Ω respectively).

1.1 Draw the electric circuit diagram

1.2 Calculate the equivalent resistance of the circuit.

1.3 Calculate the current flowing through the circuit.

1.4 Calculate the voltage across each resistor.

1.5 Explain the current flowing through each resistor.

Question 2

An electric circuit has the following: A 8V battery, a switch, an ammeter and three resistors in parallel (2, 4 and 6 Ω respectively).

2.1 Draw the electric circuit diagram.

2.2 Calculate the equivalent resistance of the circuit.

2.3 Calculate the current flowing through the circuit.

2.4 Calculate the current flowing each resistor.

2.5 Explain the voltage across the resistors.

Formulas to be used:

V=IR

I=V/R

R=V/I

Rs= R1 + R2 + R3 +.....

1/Rp = 1/R1 + 1/R2 + 1/R3 + ....

The following link will be of great assistance:

Process

Step 1: Write down the differences between circuits in series and circuits in parallel

Step 2: Mathematically represent the differences

Step 3: Draw the circuit diagrams for the described circuits

Step 4: Write down relevant formulas

Step 5: Substitute values into the correct formulas

HINT: The formula for calculating the equivalent resistance is different for resistors in series and resistors in parallel

Resources:

Calculations on resistors in series and parallel:

Evaluation

The following criteria will be used for marking:

Question 1

 1.1 1 mark for correct connection of resistors 1 mark for overall  circuit diagram 1.2 1 mark for the correct formula 2 marks for the correct substitution and answer 1.3 1 mark for the correct formula (for each resistor) 2 marks for the correct substitution and answer (for each resistor) 1.4 2 marks for correct explanation

Question 2

 1.1 1 mark for correct connection of resistors 1 mark for overall  circuit diagram 1.2 1 mark for the correct formula 2 marks for the correct substitution and answer 1.3 1 mark for the correct formula (for each resistor) 2 marks for the correct substitution and answer (for each resistor) 1.4 2 marks for correct explanation

Total for assessment: 32

Conclusion

Now that you are done with this assessment, you should be able to differentiate between series and parallel connections.

For you to be able to do calculations on electric circuits, it's very important that you know the formulas and also when and how to use them.

Questions on electric circuits are usually continuous, therefore, you should be attentive in your calculations.

These two topics, resistor in series and resistors in parallel are very important. They are the building block to electric circuits that have a combination of both resistors in series and parallel. Combined circuits are a bit more complex and need one to thorough understand resistors in series and resistors in parallel.

For better understanding of electric circuits, do a lot of practice  exercises and use different sources when you study. Also, watch experiments on YouTube. If possible try doing basic experiments yourself.