Question about Amperage

[littlepigboy5]

If i have 4 5amp light bulbs connected to one relay, does the relay need to be able to support 20 amps, or just 5, or something else, and how would i calculate this myself using ohm's law in the future,

Thanks

[rmac52]

If you have 20 amps worth of light bulbs your going to need a relay that can support the 20 amps your drawing.

[littlepigboy5]

If you have 20 amps worth of light bulbs your going to need a relay that can support the 20 amps your drawing.

i realize that, thank you for the response, but the question is, if each bulb is 5 amp, is it a total of 20amps draw?

[Wano97]

i realize that, thank you for the response, but the question is, if each bulb is 5 amp, is it a total of 20amps draw?

Yes, you do

[rmac52]

i realize that, thank you for the response, but the question is, if each bulb is 5 amp, is it a total of 20amps draw?

Amp draw is cumulative. So 4 bulbs drawing 5 amps will use 20 amps. If you added a 10 amp fan to the circuit you now have a draw of 30 amps.

[Rabald]

it depends:

 

if your lamps are connected in serie = total current will be 5 amps.

so you will be fine with a relay of 5 amps

 

if you connect your lamps in parallel (most likely)= total current will be 4 x 5 amps = 20amps

so you are going to need a relay of 20 amps

 

hope that made any sense

[littlepigboy5]

it depends:

 

if your lamps are connected in serie = total current will be 5 amps.

so you will be fine with a relay of 5 amps

 

if you connect your lamps in parallel (most likely)= total current will be 4 x 5 amps = 20amps

so you are going to need a relay of 20 amps

 

hope that made any sense

that's very helpful, what is the difference between parralel and a series, plz draw it so i understand.

[Rabald]

http://www.ia470.com/primer/circt.gif  <= image that shows the difference

 

http://www.bbc.co.uk/schools/gcsebitesize/science/add_edexcel/controlling_current/circuitsrev1.shtml

and this one gives some more info aswell. (you can find a lot of info on the internet about this subject)

 

 

In short, 

parallel: each device will get the full battery voltage, the current in each loop will not be affected by another device in another loop.

 

serie: the battery voltage will split between the devices, the current will be affected by the total resistance from all devices. <= the result is: not all devices will run on max capacity.

 

== ohm's law