Thursday, 7 August 2025

Week 4 Term 3 2025 Inductors

  Basic Circuit Revision

  • Act 13A, p.205-206 Level 2 D.C. Circuit Revision


Internal Resistance of a Battery

  • Act 13B, p.210-211 Internal Resistance of a Battery

  • Ex 6B, P.261-262 Internal Resistance of a Battery


Resistor Networks (Resistors in Series and Parallel)

  • Ex 6A, p.251-253 Resistor Networks


Kirchhoff’s Laws

  • Act 13C, p.214-216 Kirchhoff's Laws

  • Ex 6C, p.267-272 Kirchhoff's Laws


Capacitors

  • Act 14A, p.240 Capacitance & Capacitors

  • Act 14B, p.244-245 Capacitor Networks & Energy

  • Act 14C, p.249-251 Charging & Discharging Capacitors

  • Ex 6D, p.277-280 Capacitor Energy

  • Ex 6E, p.283-284 Capacitors

  • Ex 6F, p.289-292 Capacitor Networks

  • Ex 6G, p.298-300 Charging & Discharging Capacitors


Inductors

  • Act 15A, p.259-260 Induced Voltage & Current

  • Act 15B, p.263-264 Transformers

  • Act 15C, p.268-269 Inductance

  • Act 15D, p.272-273 Voltage and Current Graphs for the Inductor

  • Ex 6H, p.303-305 Inductance in DC Circuits

  • Ex 6I, 308-310 Inductance: Self; Mutual; Time Constant; Energy Stored

  • Ex 6J, p.311-312 Transformers


Right Hand Screw Rule


Right Hand Slap Rule

Magnetic Flux










Lenz's Law

Faraday's Law & Lenz's Law


Inductance








Transformers


The ratio of the secondary to primary voltage is equal to the ratio of the secondary to primary turns

Vs/Vp = Ns/Np

In an Ideal Transforme
Secondary Power = Primary Power
In reality, energy is lost through heat from eddy currents generated in the soft iron core from the changing flux.

NB: As Voltage is often referred to as e.m.f. the Symbol "e" or "E" is often used in engineering to refer to e.m.f.
This is the case in the video below.
After explaining how basic Transformers work, this video goes on to explain 3-Phase Transformers.

NZ Street Step-Down Transformer

Internal Diagram of a Transformer

How Do Substations Work?

Fuse MCB, How it Works

Thursday, 31 July 2025

Week 3 Term 3 2025 Capacitors

 Basic Circuit Revision

  • Act 13A, p.205-206 Level 2 D.C. Circuit Revision


Internal Resistance of a Battery

  • Act 13B, p.210-211 Internal Resistance of a Battery

  • Ex 6B, P.261-262 Internal Resistance of a Battery


Resistor Networks (Resistors in Series and Parallel)

  • Ex 6A, p.251-253 Resistor Networks


Kirchhoff’s Laws

  • Act 13C, p.214-216 Kirchhoff's Laws

  • Ex 6C, p.267-272 Kirchhoff's Laws


Capacitors

  • Act 14A, p.240 Capacitance & Capacitors

  • Act 14B, p.244-245 Capacitor Networks & Energy

  • Act 14C, p.249-251 Charging & Discharging Capacitors

  • Ex 6D, p.277-280 Capacitor Energy

  • Ex 6E, p.283-284 Capacitors

  • Ex 6F, p.289-292 Capacitor Networks

  • Ex 6G, p.298-300 Charging & Discharging Capacitors



Capacitor
C = Q/V


Capacitors
Basic Definition
Physical Parameters
Energy Stored
Ep = ½ QV


Capacitors & Capacitance

Capacitors Explained

Dielectric

An insulating material placed in between the capacitor plates to increase the Capacitance

C = 𝜺r𝜺oA/d






Dielectrics in Capacitors

PhET Capacitor Lab Basics - App


Capacitor Circuits


Capacitors in Series
Calculating Voltage Charge and Total Capacitance

Capacitors in Parallel
Calculating Voltage Charge and Total Capacitance


Capacitors in Parallel vs Capacitors in Series


Capacitors in Combination
Series & Parallel Capacitors

Capacitors in Combination
Patrallel & Series Capacitors

Capacitors in Series
Calculating Voltage Drop


Capacitors in Series
Calculating the Charge Stored

Capacitors in Series
Calculating the Equivalent Capacitance


Capacitors in Parallel
Calculating Voltage Drop

Capacitors in Parallel
Calculating the Charge Stored


Capacitors in Parallel
Calculating the Equivalent Capacitance


Capacitor Charge & Discharge



RC Circuits 1: Charging and Discharging a Capacitor

Thursday, 24 July 2025

Week 2 Term 3 2025 Internal Resistance of a Battery & Kirchhoff's Laws

  Homework

  • Act 13A, p.205-206 Level 2 D.C. Circuit Revision
  • Act 13B, p.210-211 Internal Resistance of a Battery
  • Ex 6A, p.251-253 Resistor Networks
  • Ex 6B, P.261-262 Internal Resistance of a Battery

  • Electrical Charge

    Current
    Current is the rate of flow of Charge

    I = Δq/Δt

    Current

    Voltage
    Voltage (Potential Difference) is the change in energy (work done) to each coulomb of charge between two points on a circuit, or two points across an electric field

    Voltage
    Voltage (Potential Difference) is the change in energy (work done) to each coulomb of charge between two points on a circuit, or two points across an electric field

    V = ΔE/Q

    Ohm's Law & Resistance

    Power


    Circuit Symbols

    Ohm's Law



    Ohm's Law


    Internal Resistance of a Battery
    Batteries can be thought of as having an ideal voltage supply E.M.F. (Electromotive Force) in series with an internal resistance

    V = 𝛆 - Ir


    How to find the internal resistance of a battery

  • Kichhoff's Laws
  • Kirchhoff’s Current Law
    At any junction in a circuit, the total current entering the junction equals the total current leaving the junction
    Kirchhoff’s Voltage Law
    Around any closed path of a circuit, the total of all the potential differences, V, is zero

    Kirchhoff's Rules for Circuit Analysis - Explanation

    Kirchhoff's Rules for Circuit Analysis - Example 1

    Kirchhoff's Rules for Circuit Analysis - Example 2

    Kirchhoff's Rules for Circuit Analysis - Example 3