# Parallel and Series circuits and current

## Homework Statement

2 different questions that I'm using to test my understanding of the physics concepts rather than the math:

1)
How does the brightness of bulb A compare to that of bulb C? After D is added how does the brightness of bulb A change?
Does the brightness of B change?
Does the current through the battery change? 2) What is the current through 1, 2, 3?
What is the current through C, D, E?

## Homework Equations

Less math more conceptual, so no equations to use (plus we havent learned any equations for circuits yet)

## The Attempt at a Solution

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so for 1a I said that bulb A is brighter than bulb B/C because B & C are in parallel with each other, it increases the current through bulb A.

1b I said bulb A becomes brighter, because the addition of bulb D increases the current throughout the whole circuit. Bulb B does not change brightness because the current through its portion does not change, and the current through the battery increases since the overall current through the whole circuit increased.

For 2 I said the current through 1 is 60, equal to the bulb. For 2 I said it's 30, since 30 goes through B, which means 30 will go through C, so 30 reaches the battery equal to the bulb. For 3 I said it's 120, because D and E both have 60 mA since they're in parallel, so the total is 120.

Does my reasoning of these concepts seem good or am I off on something?

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haruspex
Homework Helper
Gold Member
All good, except how the addition of D affects B in 1. Think about the voltage drop across A.

• motyapa
I used this website to try and help me to reach my answer: http://epb.apogee.net/foe/fcspp.asp [Broken]

it seems like adding more in parallel shouldnt change how bright the other parallel ones are? I'm confused why B should change.

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haruspex