Figure 21.55 shows how a bleeder resistor is used to discharge a capacitor after an electronic device is shut off, allowing a person to work on the electronics with less risk of shock. (a) What is the time constant? (b) How long will it take to reduce the voltage on the capacitor to (5% of 5%) of its full value once discharge begins? (c) If the capacitor is charged to a voltage V0 through a 100-Ω resistance, calculate the time it takes to rise to 0.865V0 (This is about two-time constants.)
(a) The time constant is
(b) Time to reduce the voltage on the capacitor to is: .
(c) The time it takes to rise to 0.865V0 is:.
A capacitor is an electrical energy storage device that operates in an electric field. It's a two-terminal passive electrical component. Capacitance is the term used to describe the effect of a capacitor.
The following formula may be used to compute the time constant,
We will utilize anequation to determine how long it will take to drop the voltage on the capacitor to .
Hence, the time to reduce the voltage on the capacitor to is.
For charging, we'll use the following equation,
Therefore, the time it takes to rise to 0.865V0 is .
The duration of a photographic flash is related to an RC time constant, which is 0.100 µs for a certain camera. (a) If the resistance of the flash lamp is 0.0400 Ω during discharge, what is the size of the capacitor supplying its energy? (b) What is the time constant for charging the capacitor, if the charging resistance is 800 kΩ?
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