March 22, 2009
In a parallel RC circuit, does the resistor or capacitor receive more current initially?
In an RC circuit composed simply of a parallel circuit with a resistor on one branch and a resistor on another, when they are first connected with a battery, which receives more current? What is the resistance of a capacitor initially, would it be generally considered less than a lightbulb? I know eventually more current will go through the resistor as the capacitor fully charges, but I don't know what happens initially.
We really don't have enough information.
What would happen to the capacitor depends on the value of the capacitor and how quickly the voltage will rise.
While, technically, if the voltage applied rises from zero to the rated voltage (of the voltage source) in zero time, the capacitor will look as if it is a dead short, thus, assuming the voltage source has zero internal resistance, infinite amount of current will flow.
But, in reality, that is not going to happen. Any voltage source in real world has internal resistance. Aside from it, the amount of the current will depend on how quickly the voltage will raise across the capacitor.
Even if we ignore the internal resistance of the voltage source, the voltage will never rise infinitely quickly, thus the amount of current will be limited.
What would flow in the resister will be constant per ohm's law.
Which would be more? It will depend on the value of the components and the time it takes for the voltage source across the components to go from zero to the voltage applied.
Filed under RC by Ray
Comments on In a parallel RC circuit, does the resistor or capacitor receive more current initially? »
An uncharged capacitor acts as a short, so it gets all the current at first. The current falls off (goes through the resistor instead) as it charges up. Eventually, the fully charged capacitor acts like an open circuit, so the resistor gets all the current.
References :
Initially the capacitor receives more current.
References :
We really don't have enough information.
What would happen to the capacitor depends on the value of the capacitor and how quickly the voltage will rise.
While, technically, if the voltage applied rises from zero to the rated voltage (of the voltage source) in zero time, the capacitor will look as if it is a dead short, thus, assuming the voltage source has zero internal resistance, infinite amount of current will flow.
But, in reality, that is not going to happen. Any voltage source in real world has internal resistance. Aside from it, the amount of the current will depend on how quickly the voltage will raise across the capacitor.
Even if we ignore the internal resistance of the voltage source, the voltage will never rise infinitely quickly, thus the amount of current will be limited.
What would flow in the resister will be constant per ohm's law.
Which would be more? It will depend on the value of the components and the time it takes for the voltage source across the components to go from zero to the voltage applied.
References :