kuruman said:You can use the equation you have. Just think, what will the voltage across the capacitor be when it is fully charged?
RougeSun said:Homework Statement
A 1234. pF capacitor and a 5.6 × 106 ohm resistor are connected in series to 78. volts EMF. Approximately how long does it take the capacitor to become almost fully charged?
Homework Equations
Vf=Vo(1-e^(-t/RC))
The Attempt at a Solution
I'm not sure if the equation I'm using is correct. I know there is one that has Q in it but couldn't find it. If there is Q in it how do I link it to volts? Through C=Q/Z?
This is correct as it stands.lee.perrin@gm said:This is what is in the textbook
t=RC=(100k)(0.001mF)=100millisecond
lee.perrin@gm said:The mF that I have in there is microfarad. I did not have the mu sign.
And as it is I don't get that value on the calculator.
I get 0.0001sec
In an RC circuit, the capacitor is connected in series with a resistor and a voltage source. When the circuit is closed, current flows through the resistor, causing a potential difference to build up across the capacitor. This potential difference causes the capacitor to charge, storing energy in the form of an electric field between its plates.
The time constant, denoted by the symbol tau (τ), is a measure of how quickly a capacitor charges in an RC circuit. It is equal to the product of the resistance (R) and the capacitance (C) in the circuit. A larger time constant means the capacitor will take longer to charge, while a smaller time constant means it will charge more quickly.
As the capacitor charges, the voltage across it increases. At first, the voltage increases rapidly, but as the capacitor approaches full charge, the rate of increase slows down. Once the capacitor is fully charged, the voltage across it will be equal to the voltage of the source.
As the capacitor charges, the current in the circuit decreases. This is because as the voltage across the capacitor increases, the potential difference across the resistor decreases, resulting in a lower current according to Ohm's law (I = V/R). Eventually, when the capacitor is fully charged, no current will flow through the circuit.
The time constant of an RC circuit can be changed by altering either the resistance or the capacitance in the circuit. Increasing the resistance or decreasing the capacitance will result in a longer time constant, while decreasing the resistance or increasing the capacitance will result in a shorter time constant. This can affect the rate at which the capacitor charges and the voltage and current in the circuit.