# Homework Help: Difference between lights connected in series and parallel

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1. Jan 21, 2016

### prishila

1. The problem statement, all variables and given/known data

When two same lamps are connected with the same battery. Their lighting will be greater when they are connected in series or parallel?
2. Relevant equations
Series U=U1+U2+U3+...
I=I1=I2=I3...
Parallel U=U1=U2=U3...
I=I1+I2+I3+...

3. The attempt at a solution
The answer is when they are connected in parallel. But why?
Is it related to the tension or intensity or power?

2. Jan 21, 2016

### Staff: Mentor

In a very simple view, the brightness of a light bulb is proportional to the power it consumes. The power is determined by the voltage across the bulb and the current through it: $P = V I$.

If you assume that the bulb has a constant resistance (again, a simple view), then Ohm's Law tells you that the current through it is related to the voltage across it by $I = V/R$.

Use your knowledge of how voltage and current are distributed among components in series and parallel circuits.

3. Jan 21, 2016

### prishila

So we can write P=U^2/R
U is the same in each resistance in parallel, but it divides in resistances in series. So it is greater in resistances in parallel. This way P is greater when they are connected in parallel. Am I right?

4. Jan 21, 2016

### Staff: Mentor

Yes, that's a correct analysis.