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Physics 10 Online
OpenStudy (anonymous):

HELP IN PHYSICS PLEASE?

OpenStudy (anonymous):

Consider two resistors in series R1 = 5 ohms and R2 = 7 ohms. They are powered with a battery providing a potential difference of 48 volts

OpenStudy (anonymous):

How do you calculate the total current leaving source: I - current across R1: I1 - current across R2:I2 the potential drop across R1:V1 and R2:V2

OpenStudy (unklerhaukus):

\[V=IR\]

OpenStudy (unklerhaukus):

The voltage is equal to the intensity of the current multiplied by resistance

OpenStudy (anonymous):

But if im trying to find the total and theres a difference of 48 V do i use tht?

OpenStudy (unklerhaukus):

through the R_1 the current is 48V/5ohms ~ 9.5Amps

OpenStudy (anonymous):

alright so I = 9.5 all the way

OpenStudy (anonymous):

So when it asks for the current across R1: I1 it would just be 9.5

OpenStudy (unklerhaukus):

Yeah actually 9.6 Amps through the first resistor

OpenStudy (anonymous):

even when it asks the current across R2: I2

OpenStudy (unklerhaukus):

Throught the second resistor R_2 the current is \[I=V/R\] \[=I_2=48V/7\Omega\approx 6.9 Amps\]

OpenStudy (anonymous):

oh alright . but how does the potential drop work?

OpenStudy (anonymous):

nevermind the drop would be V = 9.6 x 5 V = 6.9 x 7 right?

OpenStudy (unklerhaukus):

what happens when you add those together? you should get a total of 48V

OpenStudy (anonymous):

well i get 48 + 48.3 = 9.6 ...

OpenStudy (unklerhaukus):

i think i must have said something wrong because add those give a greater potential that then the battery supplied

OpenStudy (unklerhaukus):

ah ok i see what my mistake was , sorry about this, The current in the circuit is \[I=V/(R_1+R_2)\]

OpenStudy (anonymous):

So I = V / (R1 + R2) would be the formula for finding the circuit of R1:I2

OpenStudy (anonymous):

AND finding R2:I2

OpenStudy (unklerhaukus):

The current will be the same at all point in the circuit \[I_T=\frac V R_T=48/(5+7)=4Amps\]

OpenStudy (anonymous):

thats right two last questions sorry im terrible at physics.

OpenStudy (anonymous):

how do you calculate the potential of the circuit at the point between the two resistors (R1 and before R2)

OpenStudy (anonymous):

LAST- Calculating the potential after the current traverses R2 and why?

OpenStudy (unklerhaukus):

The current is constant through out the circuit,The voltage drop across R_1 will be 4x5=20V

OpenStudy (unklerhaukus):

Because the circuit the in series\[I=I_1=I_2\]

OpenStudy (unklerhaukus):

\[V_2=4 \times 7 =28V\]

OpenStudy (anonymous):

So between the points the circuit stays the same.

OpenStudy (unklerhaukus):

yeah think of the flowing electrons, they arn't leaving the circuit at any point

OpenStudy (anonymous):

how about calculating the traverses R2

OpenStudy (unklerhaukus):

I dont know what you mean by traverse

OpenStudy (anonymous):

like calculating the potential after the current traverses R2

OpenStudy (unklerhaukus):

DO you mean what is the potential voltage across R2?

OpenStudy (anonymous):

yeah lol

OpenStudy (unklerhaukus):

\[V_2=IR\] \[=4A\times 7\Omega=28V\]

OpenStudy (anonymous):

Oh alright thank you so much! (:

OpenStudy (unklerhaukus):

So \[V_1+V_2 =V\] \[=20V+28V=48V\] all the power int the battery has gone to the potential across the resistors

OpenStudy (unklerhaukus):

\[I=I_1=I_2 = 4A\] at all points in the (series)circuit the current is the same

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