What is the unit of Farad equivalent to in terms of joules and Coulomb?
The Correct Answer and Explanation is:
The unit of capacitance, the farad (F), is defined as the amount of capacitance that allows a one-coulomb (C) charge to be stored with a one-volt (V) potential difference across the capacitor.
Mathematically, capacitance CCC is related to charge QQQ and voltage VVV through the equation:C=QVC = \frac{Q}{V}C=VQ
Now, using the definition of joule (J), which is a unit of energy, we know that:1 joule=1 coulomb×1 volt1 \, \text{joule} = 1 \, \text{coulomb} \times 1 \, \text{volt}1joule=1coulomb×1volt
This shows that joules measure energy, and volts measure potential energy per unit charge.
Combining these concepts, we can express farads in terms of joules and coulombs. Since 1 volt = 1 joule/coulomb, we substitute this into the capacitance formula:C=QV=QJC=Q×CJC = \frac{Q}{V} = \frac{Q}{\frac{J}{C}} = \frac{Q \times C}{J}C=VQ=CJQ=JQ×C
Thus, the farad (F) can be expressed as:1 farad=1 coulomb21 joule1 \, \text{farad} = \frac{1 \, \text{coulomb}^2}{1 \, \text{joule}}1farad=1joule1coulomb2
This means that 1 farad is equivalent to 1 coulomb squared per joule.
Explanation:
- Capacitance is a measure of how much charge a capacitor can hold per unit of voltage applied to it.
- A farad is a very large unit of capacitance, meaning it represents a large amount of charge being stored for a small voltage.
- Since the voltage applied to the capacitor determines how much energy is stored (Joules), and this energy depends on the amount of charge stored, the relationship shows that capacitance is tied to both charge (Coulombs) and energy (Joules).
In practical terms, capacitors typically have much smaller capacitances than 1 F because it’s an extremely large unit. Most practical capacitors are in the range of microfarads (μF, 10−6 F10^{-6} \, \text{F}10−6F) to picofarads (pF, 10−12 F10^{-12} \, \text{F}10−12F).
