Calculations

Calculations

Ohm’s Law

  • Understand that Ohm’s law states that the current through a conductor between two points is directly proportional to the voltage across the points.
  • Be able to calculate the current, voltage, or resistance in a circuit using the formula V = IR.
  • Identify how changes in current or resistance will affect the voltage in a particular circuit.

Kirchhoff’s Laws

  • Recognize the significance of Kirchhoff’s laws in circuit analysis.
  • Understand Kirchhoff’s current law (KCL), which states that the sum of currents entering a junction equals the sum of currents leaving the junction.
  • Understand Kirchhoff’s voltage law (KVL), which states that the sum of the electromotive forces in any loop must be equal to the sum of the potential drops in the loop.
  • Apply KCL and KVL to find unknown values in complex circuits.

Power Calculations

  • Be familiar with the formula for power in an electrical circuit: P = IV.
  • Understand that power is also equal to P = I²R or P = V²/R.
  • Understand power dissipation and its importance in circuit design, particularly for components like resistors and transistors.

Impedance and Reactance

  • Understand the concept of impedance, the total resistance to current flow in an AC circuit.
  • Understand reactance, the resistance offered by a capacitor or inductor to changes in current.
  • Be aware that the impedance of a series AC circuit is calculated as Z = √ (R² + X²), where R is resistance and X is reactance.

Frequency and Time Period

  • Understand the relation between frequency and time period, expressed by the equation f = 1/T.
  • Become accustomed to performing conversions between frequency (Hz) and time period (seconds).
  • Recognize that frequency determines the response of circuits, particularly in filter circuits that allow certain frequencies to pass through.

Decibels and Gain

  • Recognise that decibels (dB) are a logarithmic measure of the ratio of two values, often used to describe gain or loss in a circuit.
  • Understand the formula for calculating gain in decibels: G(dB) = 20 log (Vout/Vin) for voltage gain and G(dB) = 10 log (Pout/Pin) for power gain.
  • Remember that a positive gain denotes amplification, while a negative gain suggests attenuation.

Capacitance and Inductance Calculations

  • Understand the concepts of capacitance and inductance and their impact on circuit behaviour.
  • Know the formulas for calculating the reactance of capacitors Xc = 1/2πfC and inductors Xl = 2πfL in AC circuits.
  • Learn how to find the total capacitance in series and parallel capacitor configurations and the total inductance in series and parallel inductor configurations.