Basic concept of current, charge, voltage, Lecture notes of Electrical and Electronics Engineering

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Introduction to

Electrical and Computer

Engineering

Lecture 1

Handout 1

Introduction

Source: M. -C. Brunet (UIUC) (email: [email protected]) https://engineering.illinois.edu/directory/profile/brunet

(Positively charged) (Negatively charged)

6A

-6A

open circuit

I

I 1 is opposite of I 2 same as I 2 is same direction as I

i1 = I = 3A If R2 = R1, I2 = I1 = 3A If R2 > R1, I2 < I If R2 < R1, I2 > I

𝑸 = 𝒊 𝒕 𝒅𝒕

13 Voltage is what makes electric charges move. The voltage, or potential difference from point A to point B is the amount of energy in joules (as a result of electric field) required to move 1 coulomb of charge from point A to point B. (1V = 1J/1C) Alessandro Volta (1745 – 1827) (Italian physicist, and chemist) IV characteristic equation

What is the ground?

0V

-2V

3V

-8V

0-(-8)= 8V

-2-(-8)=6V

-8+3=-5V

-V

AB

= -(-8) = 8V

V

AB

= V

A

• V B

V

B

= V

A

• V

 AB

V

A

= V

AB

+ V

 B

V

A

– V

B

= 20V V

B

= V

D

= 0V

V

A

= V

AB

+ V

B

= 20V

V

C

= V

A

= 20V

I

I

1 (^2 ) V CD

= V

AB

= 20V

(since VC = VA, and VD = VB)

VAB IAB Ohm’s law 𝐼𝐴𝐵 = 𝑉𝐴𝐵 𝑅𝐴𝐵 (assume 𝑹𝑨𝑩 ≠ 𝟎) 𝑹𝑨𝑩 A I = 0 B

0 < V = V

AB

< 20V

Remarks:

20V

20 I 1 I 2 I 3

• V 1 -
• V 2 -  

A B

V

1

= V

2

= V

AB I (2, 4) (1, 3)

I

1

= I

2

= I

3

= I