Electrical Units

Section 1: Basic Electrical Units

  • Electrical quantities in electronics are represented by basic units of measurement such as the ampere, volt, ohm, watt, and farad.
  • Current is the rate at which charge flows through a conductor, measured in amperes (A).
  • Voltage is the potential difference between two points in a circuit and is measured in volts (V).
  • Resistance is the opposition to the flow of electric current and is measured in ohms (Ω).
  • The unit of power in a circuit is the watt (W), which is equal to one volt times one ampere.
  • Farad (F) is the unit of capacitance; a capacitor has a capacitance of one farad if it can store one coulomb of electric charge at one volt.

Section 2: Derived Electrical Units

  • Coulomb (C) is the unit of electric charge. One coulomb is equal to the charge of approximately 6.242 x 10^18 electrons.
  • Joule (J) is the unit of energy, work, or amount of heat. One joule is equivalent to one watt of power radiated or dissipated for one second.
  • Hertz (Hz) is the unit of frequency; one hertz equates to one cycle per second.
  • Decibel (dB) is the unit of signal strength, specifically the logarithmic unit of ratio between two power levels.

Section 3: Understanding the Relationships

  • Ohm’s law states a direct proportionality between voltage across an electronic component and the current through it, with resistance as the constant of proportionality. It’s represented by the formula V = I * R.
  • The power dissipated in a circuit element can be calculated using the formula P = V * I, indicating the direct relationship between voltage, current, and power.
  • Capacitance is the charge stored per volt. It is represented by the formula C = Q / V.

Section 4: Metric Prefixes

  • Electrical quantities often use metric prefixes for ease of expression. For example, milli (m), micro (μ), nano (n), pico (p), kilo (k), mega (M), giga (G), etc.
  • Milli indicates 1/1000th of a unit, micro denotes 1/1000000th, nano signifies 1/1000000000th, and pico represents 1/1000000000000th.
  • Conversely, kilo signifies 1000 units, mega denotes 1000000 units, and giga indicates 1000000000 units.

Section 5: Reading Component Values

  • Many electronic components, such as resistors and capacitors, have their values marked with a colour code or numerical code. Understanding these codes is vital in identifying component values.
  • Resistance values on resistors are usually represented with a colour code system, where each colour signifies a particular numerical value.
  • Capacitors typically use a numerical code with a combination of numbers and metric prefixes. Knowledge of these prefixes is essential to decipher the code.