Chapter 1: Introduction and DC Circuit AZRALMUKMIN BIN AZMI

Chapter 1.1: Current, Voltage, Resistance, Conductor, Insulator, Active & Passive Element AZRALMUKMIN BIN AZMI

Electric Charge (Q)  Atom: Electron (negative charge) Proton (positive charge)  The orbiting -ve charge (electron) = magnitude of +ve charge (proton)  Electric charge create electric field of forced  Electric charge is an electrical property of atomic particles of which matter consists measure in Coulombs (C)  Opposite charge = attract same charge = keep away

Electric Charge (Cont…)  1 coulomb (C) =total charge associated with x electrons.

Current (I)  Define = movement of charge in specific direction I = current (A) Q = charge (C) t = time (s) Unit = Ampere (A)

Current (I) (Cont…)  Type of current: - Direct Current (DC) current remain constant with time - Alternating Current (AC) current that varies sinusoidal with time

Current (I) (Cont…)  Current source Device that can generate a prescribe current independent of the circuit which is connected.

Voltage (V)  Define = how much energy is involve in moving a charge between 2 point in electrical system V = voltage (V) W = energy (J) Q = electric charge (C) Unit = Volt (V)

Voltage (V) (Cont…)  Voltage source Device that can generate a prescribe voltage at its terminal. Direction current is out of +ve terminal

Resistance (R)  Define = convert electrical energy to another form of energy  Resistance of any material with a uniform cross-sectional area is determined by following factor: - material - length - cross-sectional area - temperature  Unit = Ohm (Ω)

Resistance (R) (Cont…) R = resistance (Ω) ρ = resistivity (Ω-CM) l = length (CM) A = area (CM 2 )

Insulator  Define = material that have very few free electrons and required a large applied potential (voltage) to establish a measurable current level.  Material that have high resistance to current flow  Example : paper, wood, plastic, glass, mica and etc

Conductor  Define = material that permit a generous flow of electrons with very little external forces (voltage) applied.  Example : copper, aluminum, silver, iron, gold and etc  Superconductivity : Material has no resistance

Active Element  Active element : elements capable of generating electrical energy.  Example : voltage source, current source, power supply, battery VoltageCurrent

Passive Element  Passive element : elements are not capable of generating electrical energy.  Example : resistor, capacitor, inductor

Resistor (R)  Component used in circuit to control the current  Unit : Ohm (Ω)  Type of resistor : - Fixed resistor - Variable resistor  Fixed resistor : are made of metal film, high resistance wire or carbon composition

Resistor (R) (Cont…)  Variable resistor : have a terminal resistance that can be varied by tuning a dial, knob, screw or anything else appropriate for the application.

Capacitor (C)  Constructed simply of two parallel conducting plates separated by insulating material (air).  Unit : Farad (F)  A capacitor has capacitance of 1 farad if 1 coulomb of charge is deposited on the plates by a potential difference of 1 volt across the plates.

Inductor (L)  Electrical component that opposes any change in electrical current.  Composed of coil or wire wound around a non-magnetic core/magnetic core  Unit : Henry (H)  Its behavior based on phenomenon associated with magnetic field, which the source is current.