I need help with calculating volatge when using a voltmeter at a certain scale.

Question

I need help with calculating volatge when using a voltmeter at a certain scale.

I have a voltmeter with an internal resistance (R_v) of 50 k? set on the 2.5 V scale and would like to find out what voltages I would get if I were to use it to measure V_2 on a circuit like this:

I have worked out how to measure the V_2 using voltage division and parallel addition and taking into account the voltmeters internal resitance already and got:

But I don't know how the scale affects the results.

For example, what V_2 would I get if if both R_1 and R_2 were 100 ? resistors, and what V_2 would I get if if both R_1 and R_2 were 1 M? resistors? Is the equation I have applicable or should I modify it to take the scale into account?

What new equation should I use?

I have a voltmeter with an internal resistance (R_v) of 50 k? set on the 2.5 V scale and would like to find out what voltages I would get if I were to use it to measure V_2 on a circuit like this: I have worked out how to measure the V_2 using voltage division and parallel addition and taking into account the voltmeters internal resistance already and got: V2 = (Rv-1 + R2-1)-1/R1 + (Rv-1 + R2-1)-1 VB But I don't know how the scale affects the results. For example, what V_2 would I get if if both R_1 and R_2 were 100 ? resistors, and what V_2 would I get if if both R_1 and R_2 were 1 M? resistors? Is the equation I have applicable or should I modify it to take the scale into account? What new equation should I use?

Explanation / Answer

First,you need to know these things.

A voltmeter has internal resistance but usually very high, to not affect the original circuit.

So, find the voltage without using the voltmeter, i.e, r2/(r1 + r2) * Vb

Now adjust the scale of the voltmeter to some value greater than this voltage.

Then you have the right formula to proceed further.

The formula which you mentioned is absolutely correct and can be used anytime in any circuit accordingly.

Happy understanding! and do rate me high.

If you do not understand anything, please ask me, i would be glad to help you.

Related Questions

Navigate

• Browse (All)
• Browse I
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.