Electric Current and Magnetic Fields

Study Notes

Electric current: flow of electrons through a conductor
Unit: Ampere (A)
Measured using ammeters
Types of current:
- Direct Current (DC): flows in one direction
- Alternating Current (AC): flows in one direction, then reverses
Current and voltage are related by Ohm's Law: I = V/R

Magnetic field: region around a magnet or current-carrying wire where magnetic forces can be detected
Unit: Tesla (T)
Measured using magnetometers
Magnetic field lines:
- Emerges from north pole and enters south pole
- Continuous loops around a current-carrying wire
Right-hand rule: thumb points in direction of current, fingers curl in direction of magnetic field

Electromagnetic induction: production of electric current in a conductor when it moves through a magnetic field
Faraday's Law of Induction: ε = -N(dΦ/dt)
- ε: electromotive force (EMF)
- N: number of turns of coil
- Φ: magnetic flux
- d/dt: derivative with respect to time
Lenz's Law: direction of induced current is such that it opposes the change in magnetic flux

Electromagnetic wave: wave that propagates through electromagnetic field
Composed of electric and magnetic field components
Properties:
- Speed: 3 x 10^8 m/s (speed of light)
- Frequency: ranges from low radio frequencies to high gamma-ray frequencies
- Wavelength: λ = v/f
Electromagnetic spectrum:
- Radio waves
- Microwaves
- Infrared radiation
- Visible light
- Ultraviolet radiation
- X-rays
- Gamma rays

Electric circuit: path through which electric current flows
Components:
- Resistors (R)
- Capacitors (C)
- Inductors (L)
- Sources (voltage or current)
Circuit analysis:
- Series circuits: components connected one after the other
- Parallel circuits: components connected between same two points
- Kirchhoff's Laws:
  - Junction rule: sum of currents entering a junction is zero
  - Loop rule: sum of voltage changes around a loop is zero
Circuit theorems:
- Thevenin's Theorem
- Norton's Theorem
- Maximum Power Transfer Theorem

Electric current is the flow of electrons through a conductor and is measured in Amperes (A)
Ammeters are used to measure electric current
There are two types of electric current: Direct Current (DC) and Alternating Current (AC)
DC flows in one direction, while AC flows in one direction and then reverses
Ohm's Law relates current and voltage: I = V/R, where I is current, V is voltage, and R is resistance

Magnetic fields are regions around magnets or current-carrying wires where magnetic forces can be detected
The unit of magnetic field strength is the Tesla (T)
Magnetometers are used to measure magnetic fields
Magnetic field lines emerge from the north pole and enter the south pole of a magnet
Around a current-carrying wire, magnetic field lines form continuous loops
The right-hand rule relates the direction of current to the direction of the magnetic field: thumb points in the direction of current, fingers curl in the direction of the magnetic field

Electromagnetic induction is the production of electric current in a conductor when it moves through a magnetic field
Faraday's Law of Induction describes the induced electromotive force (EMF): ε = -N(dΦ/dt)
EMF is proportional to the number of turns of the coil (N), the rate of change of magnetic flux (dΦ/dt), and the derivative with respect to time (d/dt)
Lenz's Law states that the direction of the induced current is such that it opposes the change in magnetic flux

Electromagnetic waves are composed of electric and magnetic field components that propagate through the electromagnetic field
Electromagnetic waves always travel at the speed of light (3 x 10^8 m/s) in a vacuum
The frequency of electromagnetic waves ranges from low radio frequencies to high gamma-ray frequencies
The wavelength of electromagnetic waves is related to the frequency and speed: λ = v/f
The electromagnetic spectrum includes radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays, and gamma rays

Electric circuits are paths through which electric current flows
Electric circuits consist of resistors (R), capacitors (C), inductors (L), and sources (voltage or current)
Electric circuits can be classified into series circuits and parallel circuits
Kirchhoff's Laws are used to analyze electric circuits:
- Junction rule: the sum of currents entering a junction is zero
- Loop rule: the sum of voltage changes around a loop is zero
Circuit theorems include Thevenin's Theorem, Norton's Theorem, and the Maximum Power Transfer Theorem