Hey guys, new here and have a few questions that are really bugging me about caps.
1. I was under the impression, that in a simple RC circuit (voltage source in series with a cap in series with a resistor), that when you turn on the voltage source and supply a voltage difference, that the capacitor would charge itself, until the voltage across the cap (can also be said as, the differential voltage on the other pin of the cap than the voltage source) would be 0, meaning that after an RC time constant, the output of the cap would be the same voltage as the input DC voltage source.
2. Pertaining to Q1 above, I also understand that in my circuit design classes we talk about decoupling caps which block ALL dc voltage. This means that on the voltage source side of the cap, the voltage is DC, and the other side of the cap is at 0V, allowing only AC voltage to pass through. However, this cannot happen if Q1 happens... Either DC voltage is blocked, or the output voltage rises from 0V to DC at an RC time constant. Both cannot occur, obviously, so which is correct?
3. Why does a cap act as a short at high frequencies?
4. Why does a cap act as a open at low frequencies.
5. If Q2 is correct, how does a RC circuit work in DC? Seeing as how all the dc voltage is blocked by the cap, the voltage across the resistor would be 0, flowing no current through the rest of the circuit.
1. I was under the impression, that in a simple RC circuit (voltage source in series with a cap in series with a resistor), that when you turn on the voltage source and supply a voltage difference, that the capacitor would charge itself, until the voltage across the cap (can also be said as, the differential voltage on the other pin of the cap than the voltage source) would be 0, meaning that after an RC time constant, the output of the cap would be the same voltage as the input DC voltage source.
2. Pertaining to Q1 above, I also understand that in my circuit design classes we talk about decoupling caps which block ALL dc voltage. This means that on the voltage source side of the cap, the voltage is DC, and the other side of the cap is at 0V, allowing only AC voltage to pass through. However, this cannot happen if Q1 happens... Either DC voltage is blocked, or the output voltage rises from 0V to DC at an RC time constant. Both cannot occur, obviously, so which is correct?
3. Why does a cap act as a short at high frequencies?
4. Why does a cap act as a open at low frequencies.
5. If Q2 is correct, how does a RC circuit work in DC? Seeing as how all the dc voltage is blocked by the cap, the voltage across the resistor would be 0, flowing no current through the rest of the circuit.