# Circuit questionWatch

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#1
In the first set of Christmas lights lamps are connected in series, in the second set lamps are connected in series with resistors connected in parallel to each lamp, when the first lamp in each set goes out why does the rest of the lamps in the first set go out completely but the rest of the lamps in the second set just go dim? 🙂
0
1 year ago
#2
In series if one light breaks, it brakes the loop, so its not complete so electricity cant pass through. In the second set of lights the electricity can still pass through but it must go through the resistors which decreases the current ( I think) Hopefully that is correct and helps
1
#3
That helps a lot! Thank you! 😄
0
1 year ago
#4
In series the current is the same at all points in the circuit. In parallel the voltage is the same at all
points. Therefore, since the first lamp in the first set went out, current can no longer flow and the rest do not light up anymore. And when the first lamp in the second set goes off, current still flaws, but the voltage is lower so the rest of the lamps are dimmer.
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1 year ago
#5
(Original post by Freedom physics)
In the first set of Christmas lights lamps are connected in series, in the second set lamps are connected in series with resistors connected in parallel to each lamp, when the first lamp in each set goes out why does the rest of the lamps in the first set go out completely but the rest of the lamps in the second set just go dim? 🙂
In the series circuit, if one lamp fails, there is no longer a conduction path for current to flow. I = 0, and since current is the same at all points in a series circuit, all of the lamps will go out. With this type of circuit, there is no way of determining which of the lamps has failed other than pulling lamps one by one and testing them individually.

With the parallel resistor arrangement, if a lamp fails, then all current in the circuit must pass through the failed lamps parallel resistor. The total circuit resistance has increased and the circuit current must fall. All working lamps therefore dim.

In the parallel resistor arrangement, the lamp resistance is much less than each resistor. i.e. each resistor value is chosen to be around the same as the total lamp series resistance. When all lamps are working, the resistors have little effect and most current flows via the lamps. When one or more lamps fail, as previously described, all lamps dim and the owner is thus alerted to the failure. But importantly, the failed lamp does not work at all and can be immediately noticed then replaced. In other words, it's a much better engineering solution than the simple series circuit arrangement.

This is in essence, the core of design engineering - constantly developing new designs to improve operation in a real-world environment.
1
#6
Thanks! That makes a lot of sense! 😄
(Original post by uberteknik)
In the series circuit, if one lamp fails, there is no longer a conduction path for current to flow. I = 0, and since current is the same at all points in a series circuit, all of the lamps will go out. With this type of circuit, there is no way of determining which of the lamps has failed other than pulling lamps one by one and testing them individually.

With the parallel resistor arrangement, if a lamp fails, then all current in the circuit must pass through the failed lamps parallel resistor. The total circuit resistance has increased and the circuit current must fall. All working lamps therefore dim.

In the parallel resistor arrangement, the lamp resistance is much less than each resistor. i.e. each resistor value is chosen to be around the same as the total lamp series resistance. When all lamps are working, the resistors have little effect and most current flows via the lamps. When one or more lamps fail, as previously described, all lamps dim and the owner is thus alerted to the failure. But importantly, the failed lamp does not work at all and can be immediately replaced. In other words, it's a much better engineering solution than the simple series circuit arrangement.

This is in essence, the core of design engineering - constantly developing new designs to improve operation in a real-world environment.
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