EE-001

Basic Electrical Engineering Overview

Introduction

  • Definition of Electric Circuit: An electric circuit is an interconnection of electrical elements such as current, battery, and lamp.

Systems of Units

  • Comparison between English and Metric Systems of Units:

    • Length:

      • English: Yard (yd), Inch (in)

      • Metric: Meter (m), Centimeter (cm)

    • Mass:

      • English: Slug

      • Metric: Kilogram (kg), Gram (g)

    • Force:

      • English: Pound (lb)

      • Metric: Newton (N)

    • Temperature:

      • English: Fahrenheit (°F)

      • Metric: Celsius (°C), Kelvin (K)

    • Energy:

      • English: Foot-pound (ft-lb)

      • Metric: Joule (J)

    • Time:

      • Second (s) in both systems.

Unit Conversions

  • Length:

    • 1 yard = 0.914 m, 1 m = 100 cm, 1 yard = 39.37 in

  • Mass:

    • 1 slug = 14.6 kg, 1 kg = 1000 g

  • Force:

    • 1 lb = 4.45 N, 1 N = 100,000 dynes

  • Energy:

    • 1 ft-lb = 1.356 joules, 1 joule = 10^7 ergs

  • Temperature:

    • Conversions given in formulas between °F, °C, K.

SI Prefixes

  • Multiples and Submultiples:

    • 10^18 exa (E), 10^15 peta (P), 10^12 tera (T), 10^9 giga (G), 10^6 mega (M)

    • 10^3 kilo (k), 10^2 hecto (h), 10 deca (da), 10^-1 deci (d), 10^-2 centi (c)

    • 10^-3 milli (m), 10^-6 micro (μ), 10^-9 nano (n), 10^-12 pico (p), 10^-15 femto (f), 10^-18 atto (a)

Electric Charge

  • Definition: Charge is an electrical property measured in coulombs (C).

    1. The coulomb is a large unit; 1 C contains approximately 6.24 × 10^18 electrons.

    2. Charges are integral multiples of the elementary charge e = −1.602 × 10^-19 C.

    3. Conservation of Charge: Charge cannot be created or destroyed.

Electric Current

  • Definition: The rate of charge flow, measured in amperes (A).

    • Formula: i = ∆q/∆t

    • 1 ampere = 1 coulomb/second.

Direct vs. Alternating Current

  • Direct Current (DC): A current that remains constant over time.

  • Alternating Current (AC): A current that varies sinusoidally with time.

Voltage and Energy

  • Voltage: Energy needed to move a unit charge, measured in volts (V).

    • Formulas: 1 V = 1 J/C, 1 V = 1 N·m/C.

  • Energy: Capacity to do work, measured in joules (J).

    • Electric power measured in watt-hours (Wh), where 1 Wh = 3600 J.

Resistors

  • Passive vs. Active Elements: Passive elements do not generate energy; active elements do.

    • Resistance (R): Measured in ohms (Ω), defined by Ohm's law: V = IR.

    • Conductance (G): The ability to conduct current, G = 1/R.

Ohm's Law

  • States that voltage across a resistor is directly proportional to the current flowing through it:

    • V = IR

Circuit Elements

  • Series Resistors: Connected end-to-end; RT = R1 + R2 + ... + Rn.

  • Parallel Resistors: Connected across the same terminals; 1/RT = 1/R1 + 1/R2 + ... + 1/Rn.

Kirchhoff’s Laws

  • Current Law (KCL): The sum of currents entering a node is zero.

  • Voltage Law (KVL): The sum of voltages around a closed loop is zero.