Instructables
Picture of Electronics for Absolute Beginners, Chapter 3
ledbias.jpg
Welcome to Chapter 3!

In this chapter we will go through:

1. Series Circuits
2. Voltage Divider Rule
3. Applied Voltage
4. Kirchoff's Voltage Law
5. Power in Series Circuit
6. Effects of Open in Series Circuit
7. Effects of Close in Series Circuit
8. Designing a Series Circuit
 
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Step 1: Series Circuit

A series circuit is a a circuit with just one path for current to flow.

In a series circuit:

1. Resistance is additive
2. Current is constant
3. Voltage drops are additive

Click on the images attached to this lecture to see what a series circuit looks like.

Step 2: Series Circuit 2

Picture of Series Circuit 2
So if we have a circuit with 3 resistors, we want to add them to get the total resistance (RT).
Exercise 1:

R1 = 10 Ω
R2 = 50 Ω
R3 = 60 Ω

Answer:
RT = R1+R2+R3
RT = 10+50+60
RT = 120 Ω

Step 3: Series Circuit 3

Picture of Series Circuit 3
Another way of finding total resistance RT, is by using Ohm's Law. That is by dividing total voltage by total current.
RT = VT / IT

Exercise 2: A circuit has a total voltage VT of 5v and a total current IT of 2A. Find the total resistance RT.
Answer:
RT = VT / IT
RT = 5 / 2
RT = 2.5 Ω

Because current is constant or the same throughout the circuit, all we have to do is find one value of current and we can find the current for every part of the circuit.

Step 4: Series Circuit 4

Picture of Series Circuit 4
Exercise 3: A circuit has 5V, three resistors connected in series with a value of 10 Ω, 5 Ω, and 1 Ω respectively. Find the current passing through resistor one (IR1), the current passing through resistor two (IR2), the current passing through resistor three (IR3), and the total current.

Answer:
IT = VT / RT
IT = 5 / 16
IT = .3125A or 312.5mA

IR1 = 312.5mA
IR2 = 312.5mA
IR3 = 312.5mA
pcarew10 months ago
Step 6 Diagram mistakes
Voltage at point A = 100V
Voltage at point B = 60V
Voltage at point C = 0V
elektrobot (author)  pcarew10 months ago
You are absolutely correct, good catch!

Since the voltage flowing AFTER R1 (10kΩ) would only be a total of 100V. Therefore,
VR2 = (120*20)/60 = 40V

THEN, Voltage at V2 after Voltage Drop is:
V2= V1-VR2
V2= 100-40
V2= 60V

Correspondingly, the voltage flowing between R2 and R3 is 60V. Hence the equation must follow:

VR3 = (120*30)/60 = 60V

Then the voltage after passing through R3 (30kΩ) is:
V3 = V2 - VR3
V3 = 60-60
V3 = 0V
kt_0272 months ago

very comprehensive. Thx

Tinkerteem2 years ago
thanks alot i'm a beginner.. waiting for chapter 4 :)
elektrobot (author)  Tinkerteem6 months ago

thank you for your feedback.

cirvirlab1 year ago
Once when you wright your set of the equations, you can calculate it online on:

http://www.cirvirlab.com/simulation/kirch_2_real.php
elektrobot (author) 2 years ago
geeks and company,

i have been busy with work and my car lately. my next chapter will cover parallel circuits. i should be able to publish it by the end of january.

kareen.
elektrobot (author) 2 years ago
I have some complaints about the clip art I used and was asked to revise them to something related to electronics.

I think it is a reasonable request, so I shall work on finding relevant clipart for this chapter. I value all of your comments, questions and suggestions highly, and I take them all in consideration.

If you don't understand something and need further explanation, please don't be timid with your questions, i will try to answer them to the best of my knowledge.

Thanks,
Kareen
elektrobot (author)  elektrobot2 years ago
Ladies and gentlemen, I am done updating the images. You will find these images helpful in understanding the concepts introduce in this Chapter.

Thanks