CHAPTER 1 – DET 211 - Introduction to electric circuit BASIC ELECTRICAL CONCEPTS AND RESISTIVE CIRCUITS - Introduction to electric circuit - SI Unit, Electrical Unit - Electric Charge, Current, Voltage, Resistance and Power - Basic circuit elements : Active element and Passive element

Introduction to Electric Circuit Electric circuit can be defined as an interconnection between components or electrical devices for the purpose of communicating or transferring energy from one point to another. The components of electric circuit are always referred to as circuit elements.

QUANTITY AND ELECTRICAL UNIT SI Unit SI : International System of Unit that had been introduced by National Bureau of Standards in 1964 Quantity Basic Units Symbol Length Meter m Mass Kilogram kg Time Second s Electric Current Ampere A Temperature Kelvin K Luminous intensity candela cd

SI unit consists of decimal system that connected to the smaller or bigger of basic unit and by using prefix for the power of tenth: Multiplier Prefix Symbol 1018 Exa E 1015 Peta P 1012 Tera T 109 Giga G 106 Mega M 103 Kilo k 102 Hector h 101 Deka da 10-1 Deci d 10-2 Centi 10-3 Mili m 10-6 Micro  10-9 Nano n 10-12 Pico p 10-15 Femto f 10-18 Atto a

The derived unit commonly used in electric circuit theory

ELECTRIC CHARGE Polarity: type of charge (-ve or +ve) Electron: -ve charge Proton: +ve charge Electric charge create electric field of force Electric charge is an electrical property of the atomic particles of which matter consists measured in coulombs (C).

Continued… The charge e on one electron is negative and equal in magnitude to 1.602  10-19 C which is called as electronic charge. The charges that occur in nature are integral multiples of the electronic charge.

Base Unit is Coulomb (C) ELECTRIC CHARGE Quantity is Charge (Q) Base Unit is Coulomb (C) Examples of correct usage: Charge = 10 Coulombs Q = 10 C

Current is defined as the movement of charge in a specified direction.

Electric Current Terminology Quantity is Current (I) Base Unit is Ampere (A) An Ampere = Coulomb per second Examples of usage: Current = 10 Amperes I = 10 A

Electric Current Relationships Charge Q Current = I = t Time Electric current i = dq/dt. The unit of ampere can be derived as 1 A = 1C/s. Examples: Q 10 C = 2 A I = = t 5 s

Direct current (arus terus) TYPES OF CURRENT Alternating current (arus ulangalik) Direct current (arus terus) A direct current (dc) is a current that remains constant with time. An alternating current (ac) is a current that varies sinusoidally with time. (reverse direction)

A conductor has a constant current of 5 A. Example A conductor has a constant current of 5 A. How many electrons pass a fixed point on the conductor in one minute?

Total no. of charges pass in 1 min is given by Solution Total no. of charges pass in 1 min is given by 5 A = (5 C/s)(60 s/min) = 300 C/min Total no. of electronics pass in 1 min is given

Voltage is the electric pressure or force that causes current. It is a potential energy difference between two points. It is also known as an electromotive force (emf).

Quantity is Voltage (V) Voltage Terminology Quantity is Voltage (V) Base Unit is Volt (V) A Volt = Joule per second Examples of usage: Voltage = 20 Volts V = 20 V

Voltage Relationships Energy W V = Voltage = Charge Q Examples: W 24 J = 6 V V = = Q 4 C

Resistance is the opposition a material offers to current. Resistance is determined by: Type of material (resistivity) Temperature of material Cross-sectional area Length of material

Resistance Terminology Quantity is RESISTANCE (R) Base Unit is OHM (W) An ohm = Volt per ampere Example of usage: Resistance = 14 ohm R = 14 Ω

Resistance Relationships Resistivity x length KL Resistance = R = A area Example: KL 1.4 x10-6 W· cm x 5 x104 cm R = = A 2 cm2 = 5 W

Power is the rate of using energy or doing work. Work (W) Energy (W) consists of a force moving through a distance. is the capacity to do work. Joule (J) is the base unit for both energy and work.

Power Terminology Example of usage: Quantity is POWER (P) Base Unit is WATT (W) A watt = Joule per second Example of usage: Power = 200 Watts P = 200 W

Power Relationships Energy W Power = P = t Time Example: W 200 J

ACTVIVE ELEMENT AND PASSIVE ELEMENT Active Element– elements capable of generating electrical energy. For example: Voltage source Current source Passive Element – elements are not capable of generating electrical energy. For example: Resistor (dissipates energy) Capacitor and Inductor (can store or release energy)

Independent source Current Voltage This source maintains a specified voltage between its terminals but has no control on the current passing through it. The symbol of the independent voltage source is a plus-minus sign enclosed by a circle. Current This source maintains a specified current through its terminals but has no control on the voltage across its terminals. The symbol of the independent current source is an arrow enclosed by a circle. Voltage

R Circuit symbol of resistor UNIT: Ohm (Ω) Resistor is passive element that dissipates electrical energy. Linear resistor is the resistor that obeys Ohm’s law. R UNIT: Ohm (Ω)

Resistor colour code

Resistor Colour Codes Yellow 4 7 Violet 00 Red ±10 % Silver

C UNIT: Farad (F) CAPACITOR Electrical component that consists of two conductors separated by an insulator or dielectric material. Its behavior based on phenomenon associated with electric fields, which the source is voltage. A time-varying electric fields produce a current flow in the space occupied by the fields. Capacitance is the circuit parameter which relates the displacement current to the voltage.

A capacitor with an applied voltage Plates – aluminum foil Dielectric – air/ceramic/paper/mica Plates – aluminum foil Dielectric – air/ceramic/paper/mica

Circuit symbols for capacitors (a) Fixed capacitor (b) Variable capacitor

The amount of charge stored, q = CV. Circuit parameters The amount of charge stored, q = CV. C is capacitance in Farad, ratio of the charge on one plate to the voltage difference between the plates. But it does not depend on q or V but capacitor’s physical dimensions i.e.,  = permeability of dielectric in Wb/Am A = surface area of plates in m2 d = distance between the plates m

L INDUCTOR UNIT: Henry (H) Electrical component that opposes any change in electrical current. Composed of a coil or wire wound around a non-magnetic core/magnetic core. Its behavior based on phenomenon associated with magnetic fields, which the source is current. A time-varying magnetic fields induce voltage in any conductor linked by the fields. Inductance is the circuit parameter which relates the induced voltage to the current.

Typical form of an inductor

Dah tak boleh terima dah! Tolong En Hatta, Dah tak boleh terima dah!