How do capacitors eventually behave like circuit breakers?

Question

any help would be appreciated. i am a student in college taking non calc based p2 who is premed. test is tmrw and i want to fully understand this concept :)

Answer 1

They wouldn't, a capacitor is like a battery to store a charge of voltage to be utilized somewhere else, some are used to tap the ripple out of a power supply, some to offset the inductance in a circuit for power factor concepts, A circuit breaker is for protection of wires, and motors, and electric processes,

Answer 2

If a discharged capacitor is suddenly attached (via switch, for example) to a DC voltage source, current will surge to a peak value.  As the capacitor charges over time, less and less current is required.  Once the capacitor is fully charged, it no longer draws any current - thus appearing like an open circuit breaker.

You can calculate the time using the RC time constant.  Multiply the resistance in ohms of the wire or circuit used to charge the capacitor, by the capacitance in farads.  Then multiply by 5 to get approximately 99% charged.

Answer 3

Capacitors store charge, and thus energy.  Assuming a capacitor starts uncharged, when the circuit is engaged, a potential difference (voltage difference) exists across the capacitor.  In an idealized case, the capacitor has no resistance, and thus it gains charge.  This reduces the potential difference across the capacitor.  This continues until the capacitor is "fully charged."  This means that the charge on the capacitor is equal and opposite of the applied charge.  The total voltage across the capacitor is then 0V, which means no voltage flows.  Thus, if a capacitor is placed in a circuit, current initially flows but then stops and makes an open circuit.  This makes them look like circuit breakers in the sense that they will open the circuit after a certain amount of charge flows.  However, they are inappropriate to use exactly in place of a circuit breaker because they open when the total charge is large enough, but circuit breakers open when the current (charge/time) exceeds a threshold value.

Answer 4

they don't. where did you get that idea?

A circuit breaker opens a circuit when the current passes a preset limit.

A capacitor stores charge.

Answer 5

If you throw a capacitor or a circuit breaker out of the window, each will accelerate at the same rate. Eventually, each will smash on the ground.

So the behavior of these two devices under the stated conditions is pretty much identical.

Answer 6

I think there are two answers possible to this.

1) When DC is applied, the capacitor may pass a small transient, but after that will behave like an open circuit. So you could think of a capacitor as a "DC only" circuit breaker that passes AC. That's a terrible analogy, but you could make the case.

2) If you put more voltage than the capacitor can handle (hopefully more than it is rated at) the capacitor will fail. Now the problem with this is that different kinds of capacitors have different failure modes so while an electrolytic might open, some other types might short.

Answer 7

Capacitor when series with any AC circuit,it behaves like a current limitter, but it shall not completely open circuit like a circuit breaker does when overload occurs. It limits the AC current when overloaded.

Answer 8

The only way to get a capacitor to open a circuit is to over load the capacitor, or to reverse the polarity of a voltage applied to it. Reverse polarity would apply to a DC circuit. Other than that, a capacitor doesn't work like a circuit breaker.

Now, if you are thinking about blocking DC, that is a whole different matter. A capacitor is, for all intents and purposes, 2 metal plates with a gap between them. While an AC voltage will cross by the gap, DC will not. In this case, as just described, you could call a capacitor a "circuit breaker" because it does stop DC. Be careful of what terms you use to describe certain device functions.