- #1

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Why is the potential at X , denoted by V, not

V/8 = 4.8/(4.8+7.6) ? Why is numerator of resistance part 7.6 and not 4.8 by potential divider principle?

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- Thread starter vadevalor
- Start date

- #1

- 35

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Why is the potential at X , denoted by V, not

V/8 = 4.8/(4.8+7.6) ? Why is numerator of resistance part 7.6 and not 4.8 by potential divider principle?

- #2

tiny-tim

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conventionally, the current flows from the positive terminal (long line) to the negative terminal (short line)

(the

so the short line is at zero potential, and you have to

(see eg "Electric Potential Diagrams" at http://www.physicsclassroom.com/class/circuits/u9l1c.cfm)

ie you go through the 7.6Ω, so 7.6 is in the numerator

- #3

- 998

- 15

The equivalent circuit is a voltage supply of 8V connected to 4.8Ω in series with 7.6Ω as shown correctly in your diagram.

Hence 8V is the voltage on (4.8 + 7.6)Ω.

And the voltage on 4.8Ω can be found be using direct proportion.

- #4

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I have another question regarding potential could you guys help me? Answer is A but i dont understand the solution as there are 'conflicting battery direction' and i dont know how to start

Thanks!!

- curious lost soul

- #5

tiny-tim

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Answer is A but i dont understand the solution as there are 'conflicting battery direction' and i dont know how to start

start by replacing the three batteries by one 3V battery …

what is the potential at Y? and where is that measured from?

and now adjust that to start from X instead

- #6

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hi vadevalor!

start by replacing the three batteries by one 3V battery …

what is the potential at Y? and where is that measured from?

and now adjust that to start from X instead

Should i put the 3v battery to the right or left of X and should i go from + terminal to -terminal from X to Y like current flow or electron flow?

Smiles :D

- #7

tiny-tim

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Should i put the 3v battery to the right or left of X and should i go from + terminal to -terminal from X to Y like current flow or electron flow?

Smiles :D

you must always

X is somewhere in the

- #8

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hi vadevalor!

you must alwaysalwaysALWAYSuse current flownotelectron flow!

X is somewhere in themiddleof the 3V battery, isn't it?

Think i got it! Yes! So its 2-1.5= 0.5v following current direction. But when do i know to use current or electron flow direction? Above for potential divider i was told to look at electron flow

- #9

tiny-tim

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you've split the batteries into two: a 2V and a 2 minus 1 = 1V battery

so it's easy to see whether to add or subtract

Above for potential divider i was told to look at electron flow

i don't understand that …

it's *always* current flow

what exactly did they say?

- #10

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conventionally, the current flows from the positive terminal (long line) to the negative terminal (short line)

(theelectrons, of course go theotherway,towardsthe positive!)

so the short line is at zero potential, and you have tostart from the short lineto get to X to find the potential at X, ie the potential difference from zero

(see eg "Electric Potential Diagrams" at http://www.physicsclassroom.com/class/circuits/u9l1c.cfm)

ie you go through the 7.6Ω, so 7.6 is in the numerator

Its the third paragraph from your first answer :) starting from the short line (electron flow direction)

- #11

tiny-tim

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Its the third paragraph from your first answer :) starting from the short line (electron flow direction)

ah, i see, you're interpreting the flow direction as the direction for measuring the potential

no, the flow direction (= the current direction) is the direction the charge is moving (which we assume is a positive charge, so the opposite of the electron flow direction)

since the charge moves from high to low potential, the potential

ie we use a

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