Electronics for Dogs II · 10 October 05
In part II of Electronics for Dogs we consider resistance and how it really isn’t all that futile.
Sometimes resistance is very useful other times we’d prefer to minimize it. AGM batteries, for example, have very low internal resistance as compared to lead acid batteries. This allows high currents to go in and out of the battery without generating equally high levels of heat. Good for quick charging and quick get-aways.
On the other hand if you install an electric heater you are counting on resistance to do some selective heating and warm things up in the car come winter.
Whenever you attach a connector to a wire there is a small amount of resistance. Hopefully if you do it right this resistance is insignificant. A bad connector on a main battery line can quickly turn into a molten pile of metal when your EV tries to draw hundreds of amps of current through it.
By the way if you were going to make the example circuit with battery and LED you’d most likely also need to add a resistor, just like the cat suggests. LEDs can only handle a certain amount of current, so a resistor is put between it and the battery to limit how much current flows. For example a 5vdc circuit might use a 330 ohm resistor. Divide the battery voltage by the LED’s current rating to get resistance. Let’s say we wanted to hook up a super bright LED to our 12volt car battery. 12 / 0.03 = 400 ohms.
Nowadays you can buy LEDs or LED bulb packages that are designed for a certain voltage and already have the resistance built in. Check out these LEDS.
Now on to Electronics for Dogs Part III