1.2 D.C Circuits

• The DC circuit: current, voltage, resistance, and resistors
• Ohm's law (V = I x R)
• Kirchhoff's laws (current and voltage)
• Series and parallel resistor networks
• Troubleshooting DC circuits (open circuit, short circuit, faulty components)

• describe the properties of resistors in DC circuits
• analyse a DC circuit using circuit laws
• construct resistor networks in DC circuits
• troubleshoot DC circuits in electrical appliances
• appreciate the practical application of DC circuits in day-to-day life

“How do DC electric circuits work?”

“What are the applications of DC circuits in day-to-day life?”

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1. DC circuits
   40 min · 1 practice tasks · quiz
   How a DC circuit works - current, voltage, resistance and resistors; Ohm's law and Kirchhoff's laws; series and parallel resistor networks; troubleshooting faults; and everyday applications.
2. Current, voltage and resistance
   40 min · 1 practice tasks · quiz
   The three DC quantities, their units, and how a complete loop in a Kenyan torch makes the lamp light.
3. Properties of resistors
   40 min · 1 practice tasks · quiz
   What a resistor is, colour-code value, power rating, tolerance, and why those properties matter in a DC circuit.
4. Ohm's law
   40 min · 1 practice tasks · quiz
   Ohm's law V = I x R, the triangle, the straight V-I graph, and a first torch calculation.
5. Using Ohm's law
   40 min · 1 practice tasks · quiz
   More Ohm's law practice: milliamps, kilohms, a current-limit resistor for an LED, and checking a result for sense.
6. Kirchhoff's current law
   40 min · 1 practice tasks · quiz
   Current in equals current out at a junction, with torch-board and boda-light examples and a worked split.
7. Kirchhoff's voltage law
   40 min · 1 practice tasks · quiz
   Around a closed loop the voltage drops add to the supply, with a two-resistor series calculation.
8. Series resistor networks
   40 min · 1 practice tasks · quiz
   One path, same current, resistances add, voltage shared; construct and calculate a three-resistor string.
9. Parallel resistor networks
   40 min · 1 practice tasks · quiz
   Separate paths, same voltage, current splits, total R is less; house wiring and a two-branch calculation.
10. Series-parallel networks
    40 min · 1 practice tasks · quiz
    Reduce a mixed network: collapse parallel groups, add series parts, then find branch currents with Ohm, KCL and KVL.
11. Constructing resistor networks
    40 min · 1 practice tasks · quiz
    Practical build of series, parallel and one mixed network, with meter checks against calculated values.
12. Cells in DC circuits
    40 min · 1 practice tasks · quiz
    A cell as the DC source; series cells in a torch add voltage; a solar lantern pack stores DC for the LED.
13. Analysing a DC circuit
    40 min · 1 practice tasks · quiz
    Bring Ohm, KCL and KVL together on one torch-and-resistor circuit and one mixed board.
14. Open and short circuits
    40 min · 1 practice tasks · quiz
    Opens stop current; shorts bypass the load and overheat; other faults are dry joints, wrong parts and reverse cells.
15. Tracing faults in DC circuits
    40 min · 1 practice tasks · quiz
    A meter order for a dead torch or solar lantern: visual, source voltage, continuity, then voltage along the path.
16. DC circuits in daily life
    40 min · 1 practice tasks · quiz
    Torches, solar lanterns, phones, radios and vehicle electrics as everyday DC, and why the laws still apply.