Activity 11 - Ohm's Law and Resistor Values

Activity 11 - Ohm's Law and Resistor Values

Adapting the night-light circuit to be powered from a coin-cell battery.

On Saturday November 11th the students learned how to adjust the night-light circuit to use a small 3.3V coin-cell battery, rather than the 5V power supply we’ve been using to prototype the circuit on breadboards. To do this, the students were introduced to Ohm’s Law. The law relates current, voltage, and resistance, formalizing what the students have until now understood through a rock-slide analogy of electricity:


To keep the night-light LED at full brightness, the students calculated the a resistor value to use with the coin-cell battery and tested it out on the breadboard. To select this new resistor, the students also learned how to read the colour-codes of resistors.

14 boys and 24 girls attended the activity (37%:63%)1. One set of parts cost $7.66 CAD, and 10 sets were used by 38 club members, bringing the cost per student down to $2.01 CAD2.

Activity 11 was created as a Free Cultural Work and is available for use and adaption under the CC BY-SA 4.0 license:

  1. SMD has a nearly equal gender distribution among boarding students, with 175 boys and 174 girls. The gender distribution among the Himalayan Makers Guild members is 16 boys and 33 girls (33%:67%). 

  2. Part details and suppliers are given in the lesson plan.