Capacitor Charging Phase Quiz

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Questions and Answers

What happens to the transfer of electrons in a capacitor over time?

It increases exponentially over time

It is very rapid at first and slows down as time passes (correct)

It decreases exponentially over time

It remains constant throughout the charging phase

When does the transient or charging phase of a capacitor in a DC network essentially end?

When the current becomes zero

After a large amount of charge has been stored

Immediately after the switch is closed

After five-time constants have passed (correct)

What does a capacitor behave like when the switch is closed during the charging phase in a DC network?

A short circuit (correct)

A battery

An open circuit

A resistor

How is the voltage across a capacitor related to the applied voltage after five time constants in the charging phase?

Essentially equal Signup and view all the answers

What can a capacitor be replaced by once the charging phase in a DC network has passed?

An open-circuit equivalent Signup and view all the answers

When does the major change in voltage and current occur during the charging phase of a capacitor in a DC network?

During the first time constant Signup and view all the answers

What happens to the output voltage of an R-C low pass filter at high frequencies?

It is equal to zero Signup and view all the answers

In a high-pass R-C filter, what can be achieved by reversing the positions of the capacitor and resistor?

High-pass filtering Signup and view all the answers

What is a key advantage of using the unit decibel (dB) in electrical engineering?

It allows for comparisons of different levels without dealing with large numbers Signup and view all the answers

At very high frequencies, what can be substituted for the reactance of the capacitor in an electrical circuit?

Short-circuit equivalent Signup and view all the answers

At what sound level does damage to the eardrum begin according to the text?

100 dB Signup and view all the answers

What common application of the logarithmic function allows comparison of power, voltage, and other levels without working with large numbers?

Comparing levels of power and voltage Signup and view all the answers

What happens to the output voltage of a resonant electrical circuit at or near maximum response?

It is at or near maximum amplitude Signup and view all the answers

Why is it impossible for current to change instantaneously in an inductive network?

Inductive networks have time-varying magnetic fields Signup and view all the answers

What must a resonant electrical circuit have in addition to inductance to exhibit resonance?

Capacitance Signup and view all the answers

What causes sustained vibrations of very large amplitude in a mechanical system?

Mechanical resonance Signup and view all the answers

What benefit does using logarithms provide when plotting a system's response?

Facilitates plotting over a wider range of values that may be complex Signup and view all the answers

How does the use of decibels help in comparing audio levels more effectively?

By providing a common unit for comparisons Signup and view all the answers

Study Notes

R-C Filters

At low frequencies, input voltage is equal to output voltage in an R-C low pass filter.
At high frequencies, output voltage is equal to zero in an R-C low pass filter.
A high-pass R-C filter can be constructed by reversing the positions of the capacitor and resistor.
At very high frequencies, the reactance of the capacitor is very small, and the short-circuit equivalent can be substituted, resulting in Vo = Vi.
At f = 0 Hz, the reactance of the capacitor is quite high, and the open-circuit equivalent can be substituted, resulting in Vo = 0V.

Tuning and Resonance

The tuning process is the reason for the terminology "tuned circuit".
When the response is at or near the maximum, the circuit is said to be in a state of resonance.
A resonant electrical circuit must have both inductance and capacitance.
Resistance will always be present due to the lack of ideal elements or to control the shape of the resonance curve.
Mechanical impulses applied to a mechanical system at the proper frequency will cause the system to enter a state of resonance.

Capacitors

The voltage across a capacitor in a dc network is essentially equal to the applied voltage after five time constants of the charging phase.
The transient or charging phase of a capacitor has essentially ended after five-time constants.
The current of a capacitive dc network is essentially zero amperes after five time constants of the charging phase.
During the charging phase, the major change in voltage and current occurs during the first time constant.
A capacitor can be replaced by an open-circuit equivalent once the charging phase in a dc network has passed.
An ideal capacitor does not dissipate any of the energy supplied to it, storing it in the form of an electric field between the conducting surfaces.

Inductors

The inductor takes on the characteristics of an open circuit at the instant the switch is closed.
The current cannot change instantaneously in an inductive network.

Superposition Theorem

The superposition theorem is one of the most powerful in this field.

Decibel (dB)

The unit decibel (dB) is used to define levels of audio, voltage gain, energy, field strength, and so on.
The decibel is defined by a logarithmic expression.
Normal conversation occurs at about 60 dB, while damage to the eardrum can begin at 100 dB and higher.
The use of bel (B) and decibel (dB) is in recognition of Alexander Graham Bell's research and development of electronic devices.

Logarithmic Function Applications

The response of a system can be plotted for a range of values that may otherwise be impossible or unwieldy with a linear scale.
Levels of power, voltage, and the like can be compared without dealing with very large or very small numbers.
A number of systems respond to outside stimuli in a nonlinear logarithmic manner.
The response of a cascaded or compound system can be rapidly determined using logarithms if the gain of each stage is known on a logarithmic basis.

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Description

Test your knowledge on the charging phase of a capacitor in a DC network, focusing on the rate of electron transfer, voltage across the capacitor, and current behavior over time constants.