Light bulbs in series vs parallel circuits in home.

[reallyspeedly]

Hi,

I had a question in my head that turned out to two and then BANG im confused.
I need help with calculation here and explanation to get this right. If i want to build a lamp with 20 light bulbs in a 230V home. Each light bulb is 2watt.
How much current will they take when they are in series Vs parallel. Cause the always say the the current is higher in parallel circuit but how can that be possible if a lamp need let's just say 1Amp to work correctly? If i connect these in series, the more i connect the less amp.
Do i have to pick 20 11.5 volt light bulbs if i want them in series in order to make this work?
In parallel circuit i will need 20 230Volt?

 

[brianmoooore]

Do i have to pick 20 11.5 volt light bulbs if i want them in series in order to make this work?
In parallel circuit i will need 20 230Volt?

Short answer is yes, although some LED lamps are designed for use with a constant current source, rather than running from a particular voltage.
An important difference between series and parallel connection is that with parallel you can switch lamps off as desired, but with series, it's one off, all off.

 

[Lucien Nunes]

Do i have to pick 20 11.5 volt light bulbs if i want them in series in order to make this work?
In parallel circuit i will need 20 230Volt?

Correct. For TUNGSTEN FILAMENT (INCANDESCENT) LAMPS:

Total power of fixture: 20x 2W lamp = 40W.
Total current needed by fixture: 40/230 = 0.17A.
Each 2W 11.5V lamp would take 2/11.5=0.17A. The same 0.17A flows through all 20 lamps but only loses 11.5V of potential in each.
Each 2W 230V lamp would take 2/230=0.0087A. The same 230V appears across all 20 lamps but only 0.087A passes through each.

Beware: In series, although each lamp only has 11.5V across it, there will still be up to 230V to earth at one end of the chain, and 230V across any empty lamp socket, making it a shock hazard as much as 230V lamps. People don't expect to find 230V on 12V lamps. Series has complications and hazards. But, small 12V lamps are much brighter / stronger / longer lasting than small 230V lamps becayuse the filament is much shorter and thicker. Small 230V lamps are fragile and troublesome.

BUT that is for tungsten lamps. As Brian says it is not so simple with LEDs. The LED chips themselves need to be fed with a controlled current, not a controlled voltage. Some fittings use them as such, with a constant-current driver. Others use ballast resistors or built-in electronics to regulate the current from a supplied fixed voltage. E.g. you supply 12V, the internal circuit drives the LEDs with 300mA. You cannot connect this type of lamp in series. Do not assume that you can connect any constant-voltage LEDs in series without understanding what is inside.

So, as there is only 40W total needed, the best answer is probably neither of the above. Get a 12V 60W (5A) power supply unit or transformer and run 20 x 12V lamp in parallel from it. Safe, reliable, efficient.