Electric Circuits 1 - Basic Concepts

Study Notes

An electric circuit is a closed path where electrical elements are interconnected, allowing continuous flow of electric current.

Charge (q or Q): An intrinsic property of atomic particles, measured in coulombs (C).
The charge of an electron is negative, approximately -1 C, known as the electronic charge.
Electric charge is mobile, enabling transfer and conversion to other energy forms.
Current (I): Defined as the flow of electric charge created when electrons move through a conductor.
Measured in amperes (A), current has magnitude and direction, flowing from higher to lower potential.

Current (I) as a function of charge (Q) and time (t) is expressed as:
- ( I = \frac{Q}{t} )
- ( Q = I \cdot t )

Voltage (V) drives charge flow, analogous to a force causing movement.
Also known as electromotive force (emf) or potential difference; measured in volts (V), equivalent to joules per coulomb (J/C).
The electric field created by voltage between terminals forces charge carriers to move, producing current.

Power (P): Rate at which energy is absorbed or released, measured in watts (W) or joules per second (J/s).
Power relationships:
- ( P = V \cdot I )
Energy (W): Amount of energy used over time, calculated as:
- ( W = P \Delta t = V \cdot I \cdot (t_1 - t_0) )

Establishes the relationship among voltage (V), current (I), and resistance (R):
- ( V = I \cdot R )
Applies only to resistors directly connected to a voltage source.

Active Elements: Generate or supply energy (e.g., batteries).
Passive Elements: Absorb energy (e.g., resistors, capacitors).
Linear elements follow homogeneity and additivity properties; resistors exemplify linear elements.
Non-linear elements like diodes do not follow these properties.

Used to connect/disconnect circuit elements, having two states: open and closed.
Acts as a short circuit when closed and open circuit when open.

Basic calculations and considerations to find current, charge, voltage, power, and energy for various circuit configurations and scenarios are vital to understanding circuit operation and analysis.
Practice with examples helps reinforce the application of fundamental principles such as Ohm's Law, power calculations, and energy considerations in circuits.