CIRCUITS - GR11 & 12 by Lizelle Swanepoel https://padlet.com/lizellexs/y6wdalxc03r en-us 2019-09-03 10:08:56 UTC 2025-11-03 11:58:46 UTC hello@padlet.com https://padlet-assets.s3.amazonaws.com/icons/Lightdecrease.png PAST PAPERS (2015-2019) lizellexs https://padlet.com/lizellexs/y6wdalxc03r/wish/379468700 (Open this doc on iPad or laptop)]]> 2019-09-03 14:27:56 UTC https://padlet.com/lizellexs/y6wdalxc03r/wish/379468700 MEMO 2019 SUP lizellexs https://padlet.com/lizellexs/y6wdalxc03r/wish/379505812 2019-09-03 15:31:19 UTC https://padlet.com/lizellexs/y6wdalxc03r/wish/379505812 MEMO 2018 nov lizellexs https://padlet.com/lizellexs/y6wdalxc03r/wish/379506204 2019-09-03 15:32:06 UTC https://padlet.com/lizellexs/y6wdalxc03r/wish/379506204 The Magic of Electricity lizellexs https://padlet.com/lizellexs/y6wdalxc03r/wish/380042402 “La Dame de Fer” all aglow.]]> 2019-09-04 17:18:38 UTC https://padlet.com/lizellexs/y6wdalxc03r/wish/380042402 Electrical lighting facts about the Eiffel Tower lizellexs https://padlet.com/lizellexs/y6wdalxc03r/wish/380055260
  • Number of lightbulbs = 20 000
  • Power of each bulb = 6 W
  • Length of cabling = 40 km
  • The Eiffel starts twinkling: 
    1. every day, from 10 pm to 1am
    ]]>     2019-09-04 17:37:51 UTC https://padlet.com/lizellexs/y6wdalxc03r/wish/380055260     Weighting of topics in Paper 1 lizellexs https://padlet.com/lizellexs/y6wdalxc03r/wish/380270278 2019-09-05 07:11:21 UTC https://padlet.com/lizellexs/y6wdalxc03r/wish/380270278 Thinking levels in each paper lizellexs https://padlet.com/lizellexs/y6wdalxc03r/wish/380270720 2019-09-05 07:13:22 UTC https://padlet.com/lizellexs/y6wdalxc03r/wish/380270720 Formulae lizellexs https://padlet.com/lizellexs/y6wdalxc03r/wish/380282986 2019-09-05 08:03:12 UTC https://padlet.com/lizellexs/y6wdalxc03r/wish/380282986 lizellexs https://padlet.com/lizellexs/y6wdalxc03r/wish/380313531 2019-09-05 09:58:09 UTC https://padlet.com/lizellexs/y6wdalxc03r/wish/380313531 SAGS lizellexs https://padlet.com/lizellexs/y6wdalxc03r/wish/380313911 Electric circuits ]]> 2019-09-05 09:59:42 UTC https://padlet.com/lizellexs/y6wdalxc03r/wish/380313911 LOOK OUT FOR MISCONCEPTIONS ABOUT SIMPLE CIRCUITS lizellexs https://padlet.com/lizellexs/y6wdalxc03r/wish/380659296
    Students sometimes fail to discriminate between these terms and concepts:

    • Potential difference (pd) versus voltage: 
    • pd - it emphasises that we are measuring a change in “push” between two different points in an electric circuit (rather than “push” at one point).

    • Electromotive force (emf) is a term for 'voltages' across sources of electrical energy.

    • Cells becoming 'discharged' - charge is not used up, energy is transferred.

    • Conventional current:
      - This flows (by definition) from positive to negative around the external circuit 
      - Inside the cell chemical reactions ‘pump’ charge carriers to the terminals. 
      - Some may say that ‘physicists got it wrong because we now know that electrons flow the other way.’ 
      - But it is really an arbitrary choice. 
      - One can illustrate this by looking at current flow and movement of charge carriers in an electrolyte (or an ionized gas). 
      - Positive ions go one way, negative ions go the other way. 
      - And so, however current is defined, there are always examples where current direction and charge carrier movement are opposite.

    • Current flows all around a circuit: including through the cell itself.

    • A useful analogy for charge flow:
      A Bicycle Chain!
      - This transfers energy from you (equivalent to the cell) to the rear wheel.
      - The chain is not used up (neither is charge),
      - and does not disappear when you run out of energy (when the cell runs flat and the chemical reactions within it stop).
      - It has no beginning and no end.
      - It moves as a SYSTEM, every part all at once.
      - this is the CYCLIC SIMULTANEOUS MODEL OF ELECTRIC CIRCUITS. 

    • Another analogy:
    • Skiers (charges) being lifted up a mountain by a ski lift (external energy source/emf/cell) and then skiing down a slope (resistor). 
    • This is useful for the idea of voltages in parallel circuits. 
    • Parallel slopes drop different skiers through the same vertical height (equal voltages across components in parallel).
    ]]>     2019-09-05 21:03:16 UTC https://padlet.com/lizellexs/y6wdalxc03r/wish/380659296     MEMO 2017 nov lizellexs https://padlet.com/lizellexs/y6wdalxc03r/wish/380670939 2019-09-05 21:51:37 UTC https://padlet.com/lizellexs/y6wdalxc03r/wish/380670939 lizellexs https://padlet.com/lizellexs/y6wdalxc03r/wish/380671137 MEMO 2015 nov ]]> 2019-09-05 21:52:27 UTC https://padlet.com/lizellexs/y6wdalxc03r/wish/380671137 lizellexs https://padlet.com/lizellexs/y6wdalxc03r/wish/380671238 2019-09-05 21:52:54 UTC https://padlet.com/lizellexs/y6wdalxc03r/wish/380671238 MEMO 2016 Nov lizellexs https://padlet.com/lizellexs/y6wdalxc03r/wish/380671328 2019-09-05 21:53:17 UTC https://padlet.com/lizellexs/y6wdalxc03r/wish/380671328 lizellexs https://padlet.com/lizellexs/y6wdalxc03r/wish/380810263 2019-09-06 10:07:01 UTC https://padlet.com/lizellexs/y6wdalxc03r/wish/380810263 lizellexs https://padlet.com/lizellexs/y6wdalxc03r/wish/380810330 2019-09-06 10:07:23 UTC https://padlet.com/lizellexs/y6wdalxc03r/wish/380810330 lizellexs https://padlet.com/lizellexs/y6wdalxc03r/wish/380820027 2019-09-06 10:53:04 UTC https://padlet.com/lizellexs/y6wdalxc03r/wish/380820027 MEMO 2017 Sup lizellexs https://padlet.com/lizellexs/y6wdalxc03r/wish/380820140 2019-09-06 10:53:40 UTC https://padlet.com/lizellexs/y6wdalxc03r/wish/380820140 MEMO 2016 Sup lizellexs https://padlet.com/lizellexs/y6wdalxc03r/wish/380820536 2019-09-06 10:55:39 UTC https://padlet.com/lizellexs/y6wdalxc03r/wish/380820536 MEMO 2015 Sup lizellexs https://padlet.com/lizellexs/y6wdalxc03r/wish/380820623 2019-09-06 10:56:09 UTC https://padlet.com/lizellexs/y6wdalxc03r/wish/380820623 lizellexs https://padlet.com/lizellexs/y6wdalxc03r/wish/380821003 2019-09-06 10:57:52 UTC https://padlet.com/lizellexs/y6wdalxc03r/wish/380821003 WITH INTERNAL RESISTANCE IN BATTERY: lizellexs https://padlet.com/lizellexs/y6wdalxc03r/wish/382333894
  • If more resistors are added in series:
    • 1. The total resistance (𝑅T ) increases.
    2. The current in the main circuit will decrease, since the emf of the battery remains constant. (I ∝ 1/R)
    3. Vlost  will decrease, since the internal resistance remains constant. (Vlost = Ir)
      4. Vext  will increase, since the emf remains constant. (by Emf = Vext + Vlost)

    • If more resistors are added in parallel:
    1. Total resistance decreases. 
    2. Current in mains and through the battery increases. 
    3. V lost increases. (Vlost = Ir)
    4. Vext will decrease since emf stays constant. (by Emf = Vext + Vlost)

    • Graphs:
    In the graph of Vext (measured across battery) vs 𝐼 (measured in a series part of the external main circuit), the emf of the battery is given by the y-intercept (when the load current is 0 A).
    ]]>     2019-09-10 18:06:11 UTC https://padlet.com/lizellexs/y6wdalxc03r/wish/382333894     CIRCUIT PROBLEMS lizellexs https://padlet.com/lizellexs/y6wdalxc03r/wish/389847663 Engineering Circuit Analysis - Vol 1 - 10 Hour CourseVoltage, Current, Kirchhoff’s Laws, ]]> 2019-09-26 04:46:57 UTC https://padlet.com/lizellexs/y6wdalxc03r/wish/389847663 INTERNAL RESISTANCE IN A NUTSHELL lizellexs https://padlet.com/lizellexs/y6wdalxc03r/wish/390449682 WITH THE EMF FORMULA]]> 2019-09-27 09:41:37 UTC https://padlet.com/lizellexs/y6wdalxc03r/wish/390449682 INTERNAL RESISTANCE PRAC lizellexs https://padlet.com/lizellexs/y6wdalxc03r/wish/396004903 2019-10-10 07:53:07 UTC https://padlet.com/lizellexs/y6wdalxc03r/wish/396004903 Consider the equation below: lizellexs https://padlet.com/lizellexs/y6wdalxc03r/wish/396009627   
    Rearrange the equation into the form of a straight line graph  to match the quantities plotted on the graph. 
    ]]>     2019-10-10 08:10:52 UTC https://padlet.com/lizellexs/y6wdalxc03r/wish/396009627     To determine the internal resistance of a battery of cells: lizellexs https://padlet.com/lizellexs/y6wdalxc03r/wish/396011256 2019-10-10 08:16:50 UTC https://padlet.com/lizellexs/y6wdalxc03r/wish/396011256 lizellexs https://padlet.com/lizellexs/y6wdalxc03r/wish/396011985 2019-10-10 08:19:24 UTC https://padlet.com/lizellexs/y6wdalxc03r/wish/396011985 Rearranged into y = mx + c form: lizellexs https://padlet.com/lizellexs/y6wdalxc03r/wish/396013256 Emf   =  Vext  +  Ir
    Vext  =  -rI      +  Emf
       (y  =   mx    +    c)

    Where:   y-int  =  Emf
                        m  =  - r
                        x   =  I

    ]]>     2019-10-10 08:23:17 UTC https://padlet.com/lizellexs/y6wdalxc03r/wish/396013256     What is the maximum current which can be delivered by the battery? lizellexs https://padlet.com/lizellexs/y6wdalxc03r/wish/396014622
  • For max current (off the graph), Vext = 0.
  • Hence:     
    •                          Vext  =  -rI      +  Emf
                                  0  =  -rI      +  Emf
                             Emf  =  rI
                                   I  =  Emf / r 
                                      =  y-int / gradient

    ]]>     2019-10-10 08:27:07 UTC https://padlet.com/lizellexs/y6wdalxc03r/wish/396014622     SUMMARY lizellexs https://padlet.com/lizellexs/y6wdalxc03r/wish/396017135 2019-10-10 08:34:56 UTC https://padlet.com/lizellexs/y6wdalxc03r/wish/396017135 What is electricity? lizellexs https://padlet.com/lizellexs/y6wdalxc03r/wish/659138973 2020-07-21 10:27:04 UTC https://padlet.com/lizellexs/y6wdalxc03r/wish/659138973 Ammeters and Voltmeters lizellexs https://padlet.com/lizellexs/y6wdalxc03r/wish/659139072 An ammeter measures current in a circuit. 
    • An ammeter has VERY LITTLE RESISTANCE. 
    • An ammeter is always connected in SERIES with components in a circuit, as it must allow all the current to flow through it in order to measure current. 

    A Voltmeter measures potential difference between two points in a circuit. 
    • A voltmeter has GREAT RESISTANCE. 
    • A Voltemeter must therefore always be connected in parallel with a component in a circuit, in order to measure the difference in potential energy between two points right before and after a resistor. 

    ]]>     2020-07-21 10:27:13 UTC https://padlet.com/lizellexs/y6wdalxc03r/wish/659139072     lizellexs https://padlet.com/lizellexs/y6wdalxc03r/wish/659139202 2020-07-21 10:27:21 UTC https://padlet.com/lizellexs/y6wdalxc03r/wish/659139202 HOW TO CALCULATE TOTAL RESISTANCE IN SERIES VS PARALLEL lizellexs https://padlet.com/lizellexs/y6wdalxc03r/wish/659139431 2020-07-21 10:28:00 UTC https://padlet.com/lizellexs/y6wdalxc03r/wish/659139431 FURTHER CIRCUIT PROBLEMS - HOW TO SOLVE lizellexs https://padlet.com/lizellexs/y6wdalxc03r/wish/659140035 2020-07-21 10:30:03 UTC https://padlet.com/lizellexs/y6wdalxc03r/wish/659140035 Voltage drop across a resistor lizellexs https://padlet.com/lizellexs/y6wdalxc03r/wish/659140104 2020-07-21 10:30:15 UTC https://padlet.com/lizellexs/y6wdalxc03r/wish/659140104 lizellexs https://padlet.com/lizellexs/y6wdalxc03r/wish/659169716 2015 SUP

    ]]>     2020-07-21 11:58:29 UTC https://padlet.com/lizellexs/y6wdalxc03r/wish/659169716     lizellexs https://padlet.com/lizellexs/y6wdalxc03r/wish/659521283 2020-07-21 20:22:34 UTC https://padlet.com/lizellexs/y6wdalxc03r/wish/659521283 RESISTORS ADDED TO A CIRCUIT lizellexs https://padlet.com/lizellexs/y6wdalxc03r/wish/659527514
  • When resistors are added in series, the total resistance increases. 
  • When resistors are added in parallel, the total resistance decreases.
  • When a load is connected to a battery, the voltmeter connected across the battery will be the reading for 𝑉 𝑒𝑥𝑡.

    • ]]>     2020-07-21 20:31:34 UTC https://padlet.com/lizellexs/y6wdalxc03r/wish/659527514     ELECTROSTATIC VS GRAVITATIONAL FIELDS IN ACTION - BUILD YOUR OWN PARTICLE ACCELERATOR! lizellexs https://padlet.com/lizellexs/y6wdalxc03r/wish/662317883 2020-07-25 10:29:21 UTC https://padlet.com/lizellexs/y6wdalxc03r/wish/662317883 Series-parallel circuits Recap lizellexs https://padlet.com/lizellexs/y6wdalxc03r/wish/662320636 Watch this video on worked examples ]]> 2020-07-25 10:47:36 UTC https://padlet.com/lizellexs/y6wdalxc03r/wish/662320636 POWER lizellexs https://padlet.com/lizellexs/y6wdalxc03r/wish/662321566 2020-07-25 10:53:56 UTC https://padlet.com/lizellexs/y6wdalxc03r/wish/662321566