How to determine total circuit voltage and individual component resistance for a series circuit

Question

This is a question from someone who has just started to learn electronics. I'm a bit confused

Lets say I have a series circuit with three lamps. Lamp 1 needs 1V, lamp 2 needs 2V and lamp3 needs 3V. I therefore assume I need a 6V battery for this set up. However if I only have a 12V battery, presumably I would need to insert a resistor to reduce the voltage so given I need to 'remove' 6V from the circuit. This would then be 6/Current= Resistance. Do I assume that I would know the current from the battery and that this is the current throughout the circuit. Also does it matter where I put the resistor in relation to the lamps?

Answer 1

What you should figure out as well, is what the voltage difference is for your voltage source and the rating on the bulb. Your first bulb should be the 3V, as it is the highest value, which gives a voltage difference of 3V. For demonstration purposes, assume the bulb draws 0.02 amps, or 20 milliamps. Using V= I R, you find that you need a 150 ohm resistor (3/0.02). This isn't a common value resistor, so you should put some resistors in parallel or series to get the proper resistance value. You could use a 100 ohm resistor and 5 10 ohm resistors in series, or just approximate the value to get close. Since electronic parts are not perfect, you don't have to always be exact but you should still be within the ballpark. So now 3V is coming out of the bulb, but you want to reduce it to 2V. So using the same process as the first bulb, you use V= I R with V being 1 (3-2), and so on. Hope this helps! Of course, I would recommend picking up The Art of Electronics, it is a wonderful resource for learning and reviewing electronics and is fairly comprehensive.