I run an after-school program that teaches students (ages 12+) to use tools and to be mechanically self-reliant. I need help with our first of three lessons in electricity where we teach basic DC electric circuits including Ohms Law and using a digital multimeter to measure a circuit's Volts, Amps and Ohms. Then show that V=IR with those measurements. I am struggling to find a component that I can measure the resistance it will have when the circuit is active. Incandescent lamps change resistance when hot. I have not found an LED that the DMM can force past the threshold voltage. A plain resistor is boring and not a practical circuit in of itself.
Do you have any suggestions of a component we can include in this educational circuit that we can measure its resistance (outside the circuit) that it will exhibit while in an closed powered circuit? That is, when we also measure its voltage drop and current it will balance with V=IR. We specifically want to measure V,I, and R, without having to derive R from the formula. TIA. -Mr. Trainor
P.S. We will use the resistor if there is no alternative... asking the students to pretent it is a light bulb. Our non-profit is Bendix Academy.
So... These are great concerns as lamps and LEDs are non linear components. They don't behave with ohms Law.
As much as 15 year old me would love to have been taught about PN junctions and diode biasing.... I realize that other 14 year olds do not share the enthusiasm.
Heck why not?? Teach them about non linear components. It's not that terrible.
Ok, 1. use ohmmeter on LED and resistor.
Repeat with LED.. what happens... Double source voltage... but the same supply voltage, and relative higher current. Show how the LED drops a constant voltage, no matter what it's hooked up to.
Heck, you could have a simple transistor circuit to demonstrate how transistors can cause a 1 or 0 to demonstrate the very basics of computing.