Calculating ratio of voltage help

[joe007]

Homework Statement

At the given 10 Hz frequency calculate the magnitude of the voltage across a:

(1)4.7kohm resistor
(2)100nF capacitor

Homework Equations

Vr/v=R/z=R/sqrtR^2+(1/wC)

Vc/v=(1/wC)/z=(1/wC)//sqrtR^2+(1/wC)

The Attempt at a Solution

(1)4.7/sqrt(4.7^2+2*PI*4.7^2) ------i am not sure if this correct

and for part 2

(2)1/(2*PI*100*10^-9)/sqrt()

not sure of what value to use for the R

 

[MisterX]

There should be more information. What information was given about the power source? What circuit was described?

 

[joe007]

oh it had 10V power source

 

[joe007]

i think i have to calculate the voltage across each component as they are in series but not sure how to use impedance on this question

 

[NascentOxygen]

It appears that you are using as the formula for the total impedance:

z=sqrtR^2+(1/wC)

You have not derived this correctly.

You are aware that the total impedance is the sum of the impedance of R + the impedance of C. But because these individual impedances are at right angles to each other, you must add them like vectors at right angles to each other.

Complete this: the impedance of a capacitor of 100nF at 10Hz =

 

[joe007]

ok z=1/2PI*10*100*10^-9 then

 

[gneill]

ok z=1/2PI*10*100*10^-9 then

Consider using parentheses to clarify the mathematical operator precedence in your expressions. The X² and X₂ icons in the post composition header let's you create superscripts and subscripts, too. Thus:

Z_c = 1/(2*pi*10*100*10^-9)

 

[NascentOxygen]

Now, basing your calculations on a right-angled triangle, add the two series impedances.