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Adding more light bulbs in series

Student 3057 9 years ago updated by Physics Tutorial Center Staff 9 years ago 1

There is a circuit made of lights in series. Each light is like a resistor of resistance R. If we add more lights to the circuit in series, how will the brightness of the lights change? Since the current in series is always the same throughout the circuit, won't adding more lights not change the current and thus the brightness would stay the same?

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Current is the same through each element in series, however this current will change depending on what is in the circuit. When resistors are in series, they have the same effect on current as if they were all replaced by one resistor with R= sum( individual resistances ).


A battery has a defined output voltage. The voltage drop across the circuit must equal the voltage of the battery.


Since V= IR, if the total resistance increases(by adding more lights), the current must decrease(and the brightness of each light decreases).

Hope this helps!