feeling really dump...

ilan

Expert
Licensed User
Hi everyone,

I wanted to demonstrate my kids a simple electric circuit with a motor and a lamp. I remember I learned in school 25 years ago how it works but now I feel very much like this: :oops:

I was assuming that the lamp AND the motor will run as soon as I press the button but what happens is only the motor is running but the lamp is off. why is it like that? not enough power to do both? and if so why is not the lamp on and motor is off?

any explanation would be very appreciated :)

20190527_210235.jpg
 

Cableguy

Expert
Licensed User
A lamp is a resistance, that turns incandescent when a "high" enough current flow through. The motor on the other hand is an impedance, usually "high" impedance, but with a low resistance value. (That's why if you mesure résistance it will beep since it basically a long copper wire)

So, the impedance of the motor (Hall effect, I think) is preventing enough current to flow through the lamp since you have contacted them in series.
I would expect a different behaviour if connected in parallel!
 
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Star-Dust

Expert
Licensed User
Hi everyone,

I wanted to demonstrate my kids a simple electric circuit with a motor and a lamp. I remember I learned in school 25 years ago how it works but now I feel very much like this: :oops:

I was assuming that the lamp AND the motor will run as soon as I press the button but what happens is only the motor is running but the lamp is off. why is it like that? not enough power to do both? and if so why is not the lamp on and motor is off?

any explanation would be very appreciated :)

View attachment 80775
The electrical energy passes where the device does less impedance, as happens for a short circuit.
You should put a light bulb and a motor that have the same resistance in ohms, or better if you connect them in parallel and not in series.

Connecting them in parallel (lamp and motor) you will have less light intensity and fewer revolutions, but both will work
 

Star-Dust

Expert
Licensed User
A lamp is a resistance, that turns incandescent when a "high" enough current flow through. The motor on the other this an impedance, usually "high" impedance, but with a low resistance value. (That's why if you mesure résistance it will beep since it basically a long copper wire)

So, the impedance of the motor (Hall effect, I think) is preventing enough current to flow through the lamp since you have contacted them in series.
I would expect a different behaviour if connected in parallel!
You're too fast, I didn't have time to answer :D
 

ilan

Expert
Licensed User
thank now i understand. and you think that could work? i remember that in school i was teached that electricity is always seeking for the shortest distance to pass so for me in a parallel circuit i would assume that only 1 lamp will light and not all three. but i guess i am wrong?

u9l4b1.gif
 

Star-Dust

Expert
Licensed User
thank now i understand. and you think that could work? i remember that in school i was teached that electricity is always seeking for the shortest distance to pass so for me in a parallel circuit i would assume that only 1 lamp will light and not all three. but i guess i am wrong?

View attachment 80776
When it refers to a shorter path it is not meant in centimeters but relative to the resistance it finds. A greater resistance is a longer path.

But in parallel the current will divide proportionally, there is also a formula to establish it, but it is not the context to talk about this
 

Cableguy

Expert
Licensed User
Imagine the wires as water pipes… and each device (lamp and motor) as botle-necks...
in a series , the first botle neck will reduce the water flow that the next device will receive, while in paralel, all botle-neck receive the same amout of water!
Water, in this case, is current, and since both your devices are "basically" résistors, they also introduce tension-drop!
 

ilan

Expert
Licensed User
Imagine the wires as water pipes… and each device (lamp and motor) as botle-necks...
in a series , the first botle neck will reduce the water flow that the next device will receive, while in paralel, all botle-neck receive the same amout of water!
Water, in this case, is current, and since both your devices are "basically" résistors, they also introduce tension-drop!
thanx a lot cableguy and star dust. i have learned something new today :)
i wish i had listen more carefully at school 25 years ago :(
 

ilan

Expert
Licensed User
A small "payment" for all I have learned with you over the years here...
thanx cableguy, i am sure i can learn a lot from you about electricity. we spoke long time ago about that topic and you were very patient and explained it very well. i am very happy to meet people like you in the forums. :)
 

sorex

Expert
Licensed User
see serial as spreading your source over several things. a good example to remember is these electrical lights that people put in their christmas trees.

a lot of small resistance lamps don't need additional resistance or power supply.
lets say a 100 lights version where each light gets 240/100=2.4V.

parallel is equal like in a living room roof light source with 4 or more lamps where all lamps get 240V.
 
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ilan

Expert
Licensed User
then now that it is working you will add a module bluetooth to turn on/off the lamp and motor with your B4x App :)
acctually i was thinking more of an atom bomb. but maybe i will start with a simpler project.
btw has anyone created a game with b4r? if not, i will do one :)
 
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