Math Problem Statement

You measure the capacitance C1 of a capacitor by doing the following: First connect capacitors C1 and C2 in series to a power supply that provides a voltage V that can be varied. The capacitance of С2 is known to be 5.00 μF . Then vary the applied voltage V , and for each value of V measure the voltage V2 across C2 . After plotting your data as V2 versus V , you find that the data fall close to a straight line that has slope 0.650. What is the capacitance C1 ?

Solution

In this setup, we can use the relationship between the total voltage VV, the voltage across C2C_2 (which is V2V_2), and the capacitances C1C_1 and C2C_2 when they are connected in series.

Step 1: Voltage division in series capacitors

For capacitors C1C_1 and C2C_2 connected in series, the voltage across each capacitor is related to the total voltage VV by the following voltage division rule:

V2V=C1C1+C2\frac{V_2}{V} = \frac{C_1}{C_1 + C_2}

Here, V2V_2 is the voltage across C2C_2, and VV is the total voltage applied across the series combination.

Step 2: Linear relationship between V2V_2 and VV

From the given information, the plot of V2V_2 versus VV results in a straight line, implying that:

V2=mVV_2 = m \cdot V

Where mm is the slope of the line, which is given as 0.6500.650. This slope represents the fraction of the total voltage that appears across C2C_2:

m=C1C1+C2m = \frac{C_1}{C_1 + C_2}

Step 3: Solve for C1C_1

Now, we can solve for C1C_1 using the known values for mm and C2C_2:

0.650=C1C1+5.00μF0.650 = \frac{C_1}{C_1 + 5.00\, \mu F}

Multiply both sides by C1+5.00μFC_1 + 5.00\, \mu F to get:

0.650(C1+5.00μF)=C10.650 \cdot (C_1 + 5.00\, \mu F) = C_1

Expanding:

0.650C1+3.25μF=C10.650 \cdot C_1 + 3.25\, \mu F = C_1

Now, isolate C1C_1 on one side:

3.25μF=C10.650C13.25\, \mu F = C_1 - 0.650 \cdot C_1

3.25μF=0.350C13.25\, \mu F = 0.350 \cdot C_1

Solve for C1C_1:

C1=3.25μF0.350C_1 = \frac{3.25\, \mu F}{0.350}

C1=9.29μFC_1 = 9.29\, \mu F

Final Answer:

The capacitance C1C_1 is approximately 9.29 μF.


Would you like more details on this solution or have any other questions?

Here are some related questions that you might find interesting:

  1. How does the series combination of capacitors affect the overall capacitance?
  2. What would happen if the capacitors were connected in parallel instead of series?
  3. How can you calculate the total capacitance when capacitors are connected in series?
  4. What is the relationship between the voltage across capacitors in parallel and series circuits?
  5. Why does the slope of the V2V_2 versus VV graph give us information about the capacitance?

Tip: When dealing with series capacitors, remember that the total capacitance is always smaller than the smallest individual capacitor in the series.

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Capacitor Circuits
Voltage Division
Linear Relationships
Algebra

Formulas

V2/V = C1 / (C1 + C2)
V2 = m * V
m = C1 / (C1 + C2)

Theorems

Voltage Division Rule in Series Circuits

Suitable Grade Level

Grades 10-12