Unit Question with Capacitance

In summary, the conversation is about a lab involving the use of capacitors and measuring charge with the MOS FET Electrometer. The formula Q=CV is used, with C measured in Farads and V in volts. There is confusion about the unit for charge, which is answered by a clarification that 1 Farad is equal to 1 Coulomb/Volt. The original calculation is corrected to show that the unit for charge should be in nanocoulombs.
  • #1
AngelofMusic
58
0
Hello,

We haven't covered capacitance in class yet, but our lab involves the use of capacitors, so I thought I'd throw out a general question.

We were asked to use the MOS FET Electrometer to measure charge, and we were given the formula:

Q = CV

Where C is the capacitance, and V is the potential difference. C is measured in Farads and V in volts.

I'm just confused because in the sample calculations provided by the lab handout, we had:

Qinit = CV = 4.7x10^-9 [F] X 30 [V] = 141 [nF]

How come the unit for charge ended up being in nanofarads, and not in coulombs or nanocoulombs or anything like that?

Any clarifications would be appreciated!
 
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  • #2
That has to be a typo.

1 Farad is defined as 1 Coul./Volt

You have 4.7 nF x 30 V = 141 nC
 
  • #3
Okay, that makes a lot more sense.

Thanks!
 

What is capacitance and how is it measured?

Capacitance is the ability of a system to store electric charge. It is measured in units called Farads (F) and is typically denoted by the symbol C. It can be measured using a device called a capacitance meter, which measures the amount of charge that can be stored in a system at a given voltage.

What are the factors that affect capacitance?

The capacitance of a system is affected by several factors, including the distance between the two conductive plates, the area of the plates, the type of material used for the plates, and the dielectric constant of the material between the plates. These factors determine how much charge can be stored in the system at a given voltage.

What is the formula for calculating capacitance?

The formula for calculating capacitance is C = Q/V, where C is capacitance, Q is charge, and V is voltage. This formula can also be rearranged to find the charge or voltage given the capacitance.

How does capacitance affect an electric circuit?

Capacitors are often used in electric circuits to store and release energy. They can be used to smooth out voltage fluctuations, filter out unwanted frequencies, or store energy for later use. The amount of capacitance in a circuit can affect its overall behavior and performance.

What are some real-world applications of capacitance?

Capacitance has many practical applications in daily life. Some common examples include the use of capacitors in electronic devices such as computers and smartphones, power factor correction in electrical systems, and energy storage in electric cars. Capacitance is also used in sensors, touchscreens, and many other technologies.

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