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Capacitors are incredibly simple. a pair of conductive bits, separated by some dielectric media, and you just charge up that field between them until it eventually arcs if the voltage is too high. I started looking more into what material options for dielectric exist, and how changes in dielectric strength and constant. Unfortunately while reading about capacitor dielectrics I came across a comment saying that even a small air gap between two dielectric. The calculation that killed this path of DIY capacitors for magloops was that of power dissipation inside the dielectric material. I had seen tables of “tangent loss coefficient”, but thought that *those numbers seem small. With dielectric losses understood, my choices returned to an air variable capacitor, or a vacuum variable cap. Seeing that most any size. A variable capacitor is a whose capacitance may be intentionally and repeatedly changed mechanically or electronically. Variable capacitors are often used in to set the resonance frequency, e.g. to tune a radio (therefore it is sometimes called a tuning capacitor or tuning condenser), or as a variable, e.g. for in.
[PDF Version]In this case, a vacuum variable capacitor is used, rated to a peak current of 57 amps and a peak voltage of 5 kilovolts. The magnetic loop design leads to antenna which is tuned to a very narrow frequency range, giving good selectivity. However, it also requires retuning quite often in order to stay on-band.
Variable capacitors are often used in L/C circuits to set the resonance frequency, e.g. to tune a radio (therefore it is sometimes called a tuning capacitor or tuning condenser), or as a variable reactance, e.g. for impedance matching in antenna tuners.
This necessitates the careful choice of parts that can handle these voltages. In this case, a vacuum variable capacitor is used, rated to a peak current of 57 amps and a peak voltage of 5 kilovolts. The magnetic loop design leads to antenna which is tuned to a very narrow frequency range, giving good selectivity.
variable capacitor one section's capacity will increase while the other section's decreases, keeping the stator-to-stator capacitance constant. Differential variable capacitors can therefore be used in capacitive potentiometric circuits.
TA2WK (old TA1LSX), 73 High Voltage Butterfly Capacitor for Loop Antennas - TA2WK (TA1LSX): Hello Everyone, Wanna build a magnetic loop antenna? Magnetic loop antenna is a compact efficient antenna that is ideal for portable operation or limited spaces and can be improvised inexpensively.
Varicaps are used for frequency modulation of oscillators, and to make high-frequency voltage controlled oscillators (VCOs), the core component in phase-locked loop (PLL) frequency synthesizers that are ubiquitous in modern communications equipment. Variable capacitance is sometimes used to convert physical phenomena into electrical signals.
In a way, a capacitor is a little like a battery. Although they work in completely different ways, capacitors and batteries both store electrical energy. If you have read How Batteries Work, then you know that a battery has two terminals. Inside the battery, chemical reactions produce electrons on one terminal and. In this article, we'll learn exactly what a capacitor is, what it does and how it's used in electronics. We'll also look at the history of the capacitor and how several people helped shape its progress. In theory, the dielectric can be any non-conductive substance. However, for practical applications, specific materials are used that best suit the. In, a capacitor is a device that stores by accumulating on two closely spaced surfaces that are insulated from each other. The capacitor was originally known as the condenser, a term still encountered in a few compound names, such as the. It is a with two.
[PDF Version]In electrical engineering, a capacitor is a device that stores electrical energy by accumulating electric charges on two closely spaced surfaces that are insulated from each other. The capacitor was originally known as the condenser, a term still encountered in a few compound names, such as the condenser microphone.
A battery stores electrical energy and releases it through chemical reactions, this means that it can be quickly charged but the discharge is slow. Unlike the battery, a capacitor is a circuit component that temporarily stores electrical energy through distributing charged particles on (generally two) plates to create a potential difference.
Also, because capacitors store the energy of the electrons in the form of an electrical charge on the plates the larger the plates and/or smaller their separation the greater will be the charge that the capacitor holds for any given voltage across its plates. In other words, larger plates, smaller distance, more capacitance.
Because the conductors (or plates) are close together, the opposite charges on the conductors attract one another due to their electric fields, allowing the capacitor to store more charge for a given voltage than when the conductors are separated, yielding a larger capacitance.
A capacitor is characterised by its capacitance (C) typically given in units Farad. It is the ratio of the charge (Q) to the potential difference (V), where C = Q/V The larger the capacitance, the more charge a capacitor can hold.
If the voltage applied across the capacitor becomes too great, the dielectric will break down (known as electrical breakdown) and arcing will occur between the capacitor plates resulting in a short-circuit. The working voltage of the capacitor depends on the type of dielectric material being used and its thickness.
Capacitors fail due to overvoltage, overcurrent, temperature extremes, moisture ingress, aging, manufacturing defects, and incorrect use, impacting circuit stability and performance.
Some of the causes of capacitor trouble are listed below. Transient surges, incurred as a result of switching operations, malfunction of associated circuits or components when of sufficient duration and amplitude produce dielectric failure, permanent shift in capacitance, and failure of seals.
Catastrophic failure is the complete loss of function of the capacitor in a circuit. Catastrophic failure, such as open or short circuit, is the complete loss of function of the capacitor. This failure can cause the enclosure to explode, smoke, ignite, harm other electrical components, or leak liquid or gas from inside the capacitor.
Capacitors fail due to overvoltage, overcurrent, temperature extremes, moisture ingress, aging, manufacturing defects, and incorrect use, impacting circuit stability and performance. Why Capacitor is Used? Why Do Capacitors Fail? What Happens When a Capacitor Fails? How Do You Know If Your Fridge Capacitor Failure Symptoms?
Capacitor failures can be described by two basic failure categories: catastrophic failures and degraded failures. Catastrophic failure is the complete loss of function of the capacitor in a circuit. Catastrophic failure, such as open or short circuit, is the complete loss of function of the capacitor.
Rapid barometric variations may be the cause of hermetic – seal failure, with the resultant exposure of the capacitor elements to environmental conditions. High clamp pressures can also be instrumental in enclosure deformation and eventual seal failure.
Such failures can be avoided with preventive maintenance action such as replacing the capacitor. For film capacitors, the typical failure mode is capacitance decrease due to self-healing, so it is possible to diagnose the life expectancy by understanding the capacitance change.
The primary consideration for capacitor selection should be the nominal capacitance value. Knowing the application is important for determining the capacitance value. Either the designer calculates the capacitance or, in an integrated circuit application, the capacitance is recommended in the IC datasheet. Depending on. The tolerance of the capacitor is worth considering, as it gives information about the actual variation of capacitance allowed. A higher tolerance capacitor is not suitable for precision applications, and in such cases, the lowest. If the circuit or application you are dealing with is temperature-sensitive, then it is important to consider the capacitor variation versus temperature. The capacitance variation is. The voltage rating is the maximum continuous DC or AC voltagethat a capacitor can withstand without failing. Exceeding the voltage. The operating temperature is an important environmental factor in the selection of a capacitor. You can find the temperature rating of a capacitor by looking at its datasheet, and can make an appropriate selection by choosing a.
[PDF Version]When it comes to circuit boards, capacitors are widely used for various purposes, such as filtering, smoothing, and decoupling. In this comprehensive guide, we will delve into the world of capacitors on circuit boards, exploring their types, functions, and applications. What is a Circuit Capacitor?
When selecting capacitors for a circuit board, several factors need to be considered: Capacitance: Choose the appropriate capacitance value based on the specific application requirements. Voltage rating: Ensure the capacitor can withstand the maximum voltage present in the circuit.
Depending on the application, the size of the capacitor varies, either in its capacitance or physical volume. When considering the capacitor size for a given application, parameters such as voltage, current ripple, temperature, and leakage current must be considered.
Take into account the capacitance, voltage rating, ripple current rating, and temperature when selecting a capacitor. The physical size of a capacitor depends on the capacitance value. As the capacitance increases, the size becomes larger. The capacitance variation is temperature-dependent.
When sizing a capacitor, always choose one with a voltage rating higher than the maximum voltage in your circuit to prevent breakdown and damage. The capacitance value, measured in farads (F), indicates the amount of charge a capacitor can store for a given voltage.
Below are the most common types you'll encounter on circuit boards: Ceramic Capacitors: Widely used for decoupling and noise filtering. Electrolytic Capacitors: Known for higher capacitance values, commonly used in power supplies. Tantalum Capacitors: Compact and stable, often used in consumer electronics.
When the capacitance of a network whose capacitors are in series is considered, the reciprocal of the capacitances of all capacitors, is added to get the reciprocal of the total capacitance. To get this more clearly, 1CT=1C1+1C2+1C31CT=1C1+1C2+1C3 Following the same formula, if simply two capacitors are connected in. The voltage across each capacitor depends upon the value of individual capacitances. Which means VC1=QTC1VC2=QTC2VC3=QTC3VC1=QTC1VC2=QTC2VC3=QTC3 The total voltage across. The total amount of Current that flows through a set of Capacitors connected in series is the same at all the points. Therefore the capacitors. In, a capacitor is a device that stores by accumulating on two closely spaced surfaces that are insulated from each other. The capacitor was originally known as the condenser, a term still encountered in a few compound names, such as the. It is a with two.
[PDF Version]Circuit Connections in Capacitors - In a circuit, a Capacitor can be connected in series or in parallel fashion. If a set of capacitors were connected in a circuit, the type of capacitor connection deals with the voltage and current values in that network.
In a circuit, a Capacitor can be connected in series or in parallel fashion. If a set of capacitors were connected in a circuit, the type of capacitor connection deals with the voltage and current values in that network. Let us observe what happens, when few Capacitors are connected in Series.
If a set of capacitors were connected in a circuit, the type of capacitor connection deals with the voltage and current values in that network. Let us observe what happens, when few Capacitors are connected in Series. Let us consider three capacitors with different values, as shown in the figure below.
Capacitors are fundamental components in electronic circuits used to store and release electrical energy. Understanding how capacitors behave when connected in series and parallel is essential for designing efficient circuits.
In electrical engineering, a capacitor is a device that stores electrical energy by accumulating electric charges on two closely spaced surfaces that are insulated from each other. The capacitor was originally known as the condenser, a term still encountered in a few compound names, such as the condenser microphone.
Capacitor and Capacitance are related to each other as capacitance is nothing but the ability to store the charge of the capacitor. Capacitors are essential components in electronic circuits that store electrical energy in the form of an electric charge. They are widely used in various applications, What is a Parallel Plate Capacitor?
If a power outage strikes your air conditioning system and it fails to blow cold air, check: 1. The electrical panel 2. Circuit breaker 3. Circuits that run your AC's cooling system components An HVAC system needs time to reset the internal circuit breaker when a power outage happens. It may seem endless during the power outage period. During its 30-minute trial. The inner. One of the greatest threats to you and your home when a severe storm happens is lightning. When it hits a service pole, it creates power surges that destroy the power connection to your home. Once you restore power, the. If you reset the AC breaker, but the problem is still persistent, it's electrical damage. Try the following steps if your air conditioning unit has these symptoms:.
Unfortunately, our ACs suffer more from that than other electric appliances at home. Suppose your ac system isn't working after a power outage. First, you should check the circuit breaker, capacitor, or compressor. To make it easier for you. This article has spelled out possible reasons and remedies for an AC that won't work after a power outage.
Usually, during a power outage or surge, this is the first thing that gets damaged. Sadly, there is no way to get your AC unit to start working if the capacitor is not working. It is a small device that you can find attached to the external unit.
An air conditioner capacitor keeps failing when it's unable to hold a charge. This is due to one or more of the following: age, corrosion, overloading, overheating, or simply wearing out. If any of these issues are present and not addressed quickly, then the capacitor can fail completely.
Bad capacitor The capacitor in your ac unit is a small silver-like gadget that stays in the compressor (outdoor unit). It helps an ac unit to start. Unfortunately, capacitors collapse after power outages. The collapse is due to its vulnerability to power surges from time to time.
Give it half an hour to restore its internal parts after a power outage. Also, you have to look at the thermostat in your air conditioning system to see if it's off. After you've waited for half an hour or so, it's now time to power on the ac system. First, switch the ac system thermostat in its quiet mode.
A power outage can damage your air conditioner, just like a power surge can damage any electrical device or appliance. In most cases, your circuit breaker or built-in surge protection on your AC unit protects your AC and just needs a reset. But in other cases, it might be that your AC compressor or capacitor was blown during the power surge.
When a new design of power capacitor is launched by a manufacturer, it to be tested whether the new batch of capacitorcomply the standard or not. Design tests or type tests are not performed on individual capacitor rather they are performed on some randomly selected capacitors to ensure compliance of the standard. Routine test are also referred as production tests. These tests should be performed on each capacitor unit of a production batch to ensure performance parameter of individual. When a capacitor bank is practically installed at site, there must be some specific tests to be performed to ensure the connection of each unit and the bank as a whole are in order and as per specifications.
An electrolytic capacitor is actually a capacitor composed of a positive electrode (aluminum foil), a dielectric (AL2O3), and a negative electrode (electrolyte).
An electrolytic capacitor is a polarized capacitor whose anode or positive plate is made of a metal that forms an insulating oxide layer through anodization. This oxide layer acts as the dielectric of the capacitor. A solid, liquid, or gel electrolyte covers the surface of this oxide layer, serving as the cathode or negative plate of the capacitor.
The positive electrode is connected to the metal substrate with an oxide film, while the negative electrode is connected to the electrolyte through a metal electrode plate. Non-polar electrolytic capacitors, also known as bipolar electrolytic capacitors, have a dual oxide film structure.
The negative electrode in an electrolytic capacitor is connected to the electrolyte through the metal electrode plate. What is an electrolytic capacitor? Non-polar (bipolar) electrolytic capacitors adopt a dual oxide film structure, which is similar to two negative electrodes being formed by connecting them.
After forming a dielectric oxide on the rough anode structures, a counter-electrode has to match the rough insulating oxide surface. This is provided by the electrolyte, which acts as the cathode electrode of an electrolytic capacitor. Electrolytes may be "non-solid" (wet, liquid) or "solid".
A non-solid electrolyte covers the rough surface of the oxide layer, serving in principle as the second electrode (cathode) (-) of the capacitor. A second aluminum foil called "cathode foil" contacts the electrolyte and serves as the electrical connection to the negative terminal of the capacitor.
An electrolytic capacitor is a type of capacitor. The positive electrode in an electrolytic capacitor is a metal substrate with an oxide film, while the negative electrode is connected to the electrolyte (solid and non-solid) through the metal electrode plate. The positive electrode and negative electrode are the two essential components of an electrolytic capacitor.
A motor capacitor is an electrical that alters the current to one or more of a to create a rotating magnetic field. There are two common types of motor capacitors, start capacitor and run capacitor (including a dual run capacitor). Motor capacitors are used with that are in turn use.
A motor capacitor is an electrical capacitor that alters the current to one or more windings of a single-phase alternating-current induction motor to create a rotating magnetic field. [citation needed] There are two common types of motor capacitors, start capacitor and run capacitor (including a dual run capacitor).
Capacitor-start, capacitor-run motors are very similar to capacitor-start motors. The difference is that the start windings in series with a capacitor remain in the circuit while the motor is running at normal speed. Because of this, the start windings must use larger wire than that used for the split-phase or capacitor-start motors.
There are two common types of motor capacitors, start capacitor and run capacitor (including a dual run capacitor). Motor capacitors are used with single-phase electric motors : 11 that are in turn used to drive air conditioners, hot tub / jacuzzi spa pumps, powered gates, large fans or forced-air heat furnaces for example.
Capacitor problems can cause a motor not to start or to run improperly. The capacitor may open, short, or change in value to cause these problems. Under these circumstances, the capacitor will have to be replaced. Care should be taken to replace it with the original value of capacitance and voltage rating.
Two-speed capacitor-start motor using two capacitors and two start windings. The capacitors in this circuit have different values for proper operation of this type of motor. The centrifugal switch is a double-pole type that disconnects the start windings at the proper speed. Sheppard Joel Salon, in The Electrical Engineering Handbook, 2005
Some single-phase AC electric motors require a "run capacitor" to energize the second-phase winding (auxiliary coil) to create a rotating magnetic field while the motor is running.
This overcurrent relay detects an asymmetry in the capacitor bankcaused by blown internal fuses, short-circuits across bushings, or between capacitor units and the racks in which they are mounted. Each capacitor unit consist of a number of elements protected by internal fuses. Faulty elements in a capacitor unit are. Capacitors of today have very small losses and are therefore not subject to overload due to heating caused by overcurrent in the circuit. The capacitor can withstand 110% of rated voltage continuously. The capability curve then. In addition to the relay functions described above the capacitor banks needs to be protected against short circuits and earth faults. This is done with an ordinary two- or three-phase short.
Capacitor Bank Protection Definition: Protecting capacitor banks involves preventing internal and external faults to maintain functionality and safety. Types of Protection: There are three main protection types: Element Fuse, Unit Fuse, and Bank Protection, each serving different purposes.
There are mainly three types of protection arrangements for capacitor bank. Element Fuse. Bank Protection. Manufacturers usually include built-in fuses in each capacitor element. If a fault occurs in an element, it is automatically disconnected from the rest of the unit. The unit can still function, but with reduced output.
Types of Protection: There are three main protection types: Element Fuse, Unit Fuse, and Bank Protection, each serving different purposes. Element Fuse Protection: Built-in fuses in capacitor elements protect from internal faults, ensuring the unit continues to work with lower output.
The protection of shunt capacitor bank includes: a) protection against internal bank faults and faults that occur inside the capacitor unit; and, b) protection of the bank against system disturbances. Section 2 of the paper describes the capacitor unit and how they are connected for different bank configurations.
l capacitor bank utilizing internally used capa itor units. In ral, banks employing internallyFigure 1.Capacitor unit.20fused capacitor units are configured with fewer capacitor units in parallel, and more series groups of units than re used in banks employing externally fused capacitor units. The capacitor units are
Capacitor banks require a means of unbalance protection to avoid overvoltage conditions, which would lead to cascading failures and possible tank ruptures. Figure 7. Bank connection at bank, unit and element levels. The primary protection method uses fusing.
How to Desolder and Remove Capacitors From a Printed Circuit Board1. Heat Up Your Soldering Iron Plug in your soldering iron and set the temperature to around 350°C. Do the Same for the Second Leg.
Position the new capacitor leads at the holes where the old capacitor was, with the correct polarity. Just like before, press the tip of the soldering iron directly onto the joint in the back of the circuit board. As soon as the tip falls into the hole, press the wire lead through the hole, then remove the iron.
It'd be likely to grip the pcb capacitor. Warm your heat gun and push it to the capacitor's soldering back. Maintain the soldering iron in place until the capacitor separates from the circuit board. Then reverse the procedure to loosen the wire and remove the circuit board capacitor on the opposite side.
Mounting a new pcb capacitor is as important as learning to remove old and damaged capacitors. In this way, you will be able to complete the process of replacing the capacitor on the circuit board whenever you want and maintain the efficiency of the electric board properly.
Capacitors are essential components found on most circuit boards. They regulate voltage, smooth out power fluctuations, and store electrical charge. In this guide, we'll cover everything from different capacitors to how to replace them, troubleshoot problems, and find faults.
A capacitor is a basic component of a circuit board. It is responsible for storing electrical energy to help the device work properly. The capacitor may get damaged or blown away due to excessive or overheat and over-electricity. At this point, you must replace the capacitor to help the circuit board work properly.
When you witness one or more signals of a damaged capacitor that we mentioned above, you need to prepare to replace the unit. Thus, you will need the following accessories: A tool to open the device casing. Preferably, you should use a HEX wrench or screwdriver. The new capacitor ( you have to match its value with the existing capacitor)
The capacitor symbol serves to uniformly depict capacitors in electrical schematics and circuit designs. Important information about the capacitor's kind, value, and orientation in the circuit can be gleaned from its symbol. Without having to physically inspect the component, they help engineers and. Electronics experts and enthusiasts must understand capacitor symbols for numerous reasons. First, it helps them choose the right capacitor for a circuit based on its kind, value, and orientation. Second, it ensures the. The symbol of polarized capacitors contains positive and negative leads and must be LinkedIn the circuit correctly to work. These polarized capacitor symbols in circuit diagrams show their polarity and design. Circuit diagram symbols for fixed capacitors vary by kind. A fixed capacitor is usually represented by two parallel lines whose length represents its capacitance. Another typical capacitor sign is a rectangle with a straight.
[PDF Version]The capacitor symbol serves to uniformly depict capacitors in electrical schematics and circuit designs. Important information about the capacitor's kind, value, and orientation in the circuit can be gleaned from its symbol.
The ceramic capacitor symbol in circuit diagrams is represented by two parallel lines, both of which are straight, indicating the non-polarized nature of this component. This symbol is pivotal for electronic schematics due to its simplicity and ability to denote a capacitor that can be inserted in any orientation.
Standardized capacitor symbols in circuit diagrams can assists designers and manufacturers communicate effectively and consistently. Electronics experts and enthusiasts must understand capacitor symbols for numerous reasons. First, it helps them choose the right capacitor for a circuit based on its kind, value, and orientation.
The symbol of polarized capacitors contains positive and negative leads and must be linked in the circuit correctly to work. These polarized capacitor symbols in circuit diagrams show their polarity and design. 1. Aluminium Electrolytic Capacitors
There is, however, a common approach to representing them using a rectangle with one straight edge and one curved or absent edge. The schematic symbols used will vary based on the type of capacitor used and the preference of a designer; clear communication must be used, with added legends, for clarity.
The capacitor is one of the most important devices of any computer circuit and works to store and release electrical energy. A designer should know what each capacitor symbol means and what kind of capacitor it stands for when making circuit diagrams.
The AC's capacitor is used to help its compressor or fan motor turn on. Without the capacitor, the AC's motor won't be able to start rotating. So how does the capacitor work, anyway? And why is it needed? Whether it's your AC's blower, condenser fan, or compressor—all of these devices use electric motors to run. One thing. The AC's start capacitor gets the motor running, while the run capacitor helps keep the motor running smoothly. In the permanent split capacitor (PSC) motors found in most AC units,. One of the most common issues of an AC system is a bad capacitor. Here are a few different signs that your AC's capacitor might be bad: 1. Your AC's blower won't turn on 2. Your AC's. Discharging your AC's capacitor is important an important step if you're going to be testing or replacing the capacitor. Discharging a capacitor. If you have a multimeter with a capacitance testing function, then you can test your AC's capacitor. CAUTION: Capacitors contain dangerous amounts of electrical charge, so.
[PDF Version]A fan capacitor is a device that helps power motors in electric fans, air conditioners, and heat pumps. It stores energy to help the motor start up and run efficiently. The fan capacitor has two metal plates separated by a dielectric material such as oil or plastic. This creates static electricity which allows the current to flow between them.
If there is only one capacitor, it might be a dual capacitor, aka a dual run capacitor, that serves the fan motor and the compressor. Or there might be separate capacitors for each part, so two capacitors total.
A capacitor that is used to operate a ceiling fan is known as a fan capacitor. The capacitor used in a ceiling fan is a non-polarized electrolytic AC capacitor. The electrical parts of the ceiling fan include a stator, capacitor, rotor, and regulator where a capacitor plays a key role to make the fan work properly.
The AC's capacitor is used to help its compressor or fan motor turn on. Without the capacitor, the AC's motor won't be able to start rotating. So how does the capacitor work, anyway? And why is it needed? Whether it's your AC's blower, condenser fan, or compressor—all of these devices use electric motors to run.
Most ceiling fans contain two capacitors: a starting capacitor and a running capacitor. Both are called as Fan Capacitors. The start capacitor is used to give the motor an initial push while the run capacitor is used to maintain speed. However, some capacitors may have both functions.
This causes a high torque which makes the motor to rotate. The rotation of the motor increases, thus increasing its speed. The ceiling fan capacitor doesn't have a polarity so they are non-polarized capacitors. The connection of this capacitor can be done at the outside metal layer of the fan.
At its most simple, a capacitor can be little more than a pair of metal plates separated by air. As this constitutes an open circuit, DC current will not flow through a capacitor.
A capacitor is not well-described as an open circuit even in DC situations. I'd rather describe it as a charge-controlled ideal voltage source in that it can deliver and accept arbitrarily high currents at the cost of adapting its voltage depending on the delivered charge.
Capacitor: at t=0 is like a closed circuit (short circuit) at 't=infinite' is like open circuit (no current through the capacitor) Long Answer: A capacitors charge is given by Vt = V(1 −e(−t/RC)) V t = V (1 − e (− t / R C)) where V is the applied voltage to the circuit, R is the series resistance and C is the parallel capacitance.
Short Answer: Inductor: at t=0 is like an open circuit at 't=infinite' is like an closed circuit (act as a conductor) Capacitor: at t=0 is like a closed circuit (short circuit) at 't=infinite' is like open circuit (no current through the capacitor) Long Answer:
Then this is a closed circuit that will charge the capacitors. (sorry for the ascii circuit, the -| |- are capacitors, the MMM is a resistor, and the (-+) is a voltage source). Your argument is: If the circuit is open, the current must be zero. Consequently the field must be zero.
The circuit is open since the switch is open. My book says that the capacitor will only be charged when the switch is closed, but I don't see why this is true. I would expect the capacitor to be charged a little - not as much as if the circuit is closed, but still charged none the less.
Seeing it really helps you grasp what's going on. A capacitor looks like an open circuit to a steady voltage but like a closed (or short) circuit to a change in voltage. And inductor looks like a closed circuit to a steady current, but like an open circuit to a change in current.