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What will be the impedance of a C-R circuit consisting of a resistance of 20ohm and capacitance 2microfarad when it is connected to direct current?
In a direct current (DC) circuit, a capacitor will eventually charge up and act as an open circuit, meaning it will not allow current to flow after reaching full charge. As a result, the impedance of a resistor-capacitor (C-R) circuit under DC conditions is simply the resistance value. Therefore, the impedance of the given C-R circuit with a resistance of 20 ohms and a capacitance of 2 microfarads is 20 ohms.
What does the resistance in an electrical circuit limit?
Current flow. It's also worthy of noting that a resistor doesn't limit-by, it limits-to, and the current is dependent on the voltage. I[A] = U[V] / R[ohm] It's also worth to note, that the power flowing through said resistor with resistance R is I[A] * U[V] for DC circuits - helps to remember this well when picking appropriately-rated resistors for replacement. Example: let's say we have a 20-ohm, 2W resistor. If we place it in a circuit with 5V, we will get 5V / 20ohm = 250mA (0.25A) of current flowing through the resistor. The power the resistor will "see" is 250mA * 5V = 1.25W, so it's safe. But let's now put that same resistor in a 12V circuit. The current flowing will be 12V / 20ohm = 600mA (0.6A), and the power will be 600mA * 12V = 7.2W, so the resistor will burn.
