Overachieving and under-appreciated, circuits are the foundation that our technological society is built on. Now's your chance to find out not only how they work, but why. Questions regarding the physics behind voltage, resistance, capacitance, inductance, transistors, LEDs, switches, and power supplies; and how they're used to create analog and digital circuits, should be directed here.

500 Questions

What does C FAN HERM mean on a capacitor?

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Asked by Wiki User

The old capacitor was very swollen and looked like a soda can that had been repeatedly shaken up. Be sure to write down which wires go to what terminal on your capacitor before removing the old one or just take a few pictures. For home air conditioning systems that use dual run capacitors they will have 3 terminals. The terminal labeled "HERM" is for the yellow wire that goes to the "Hermetically Sealed" compressor. The "FAN" terminal gets connected to the brown wire that goes to the condenser fan. Finally the "COM" terminal is for the purple and red wires that go to the contactor and provide power to the capacitor.

What precautions must be observed in IV therapy?

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Asked by GaleEncyofMedicine

There are several precautions that should be observed in IV therapy, including:

  1. Proper hand hygiene: Healthcare providers should always wash their hands or use alcohol-based hand sanitizers before performing any IV procedure to prevent the spread of infection.

  2. Sterile technique: IV equipment and materials, including fluids, needles, and catheters, should be sterile to avoid the risk of infection. Healthcare providers should follow sterile techniques during the entire IV procedure.

  3. Correct IV line placement: The selection of the appropriate vein for IV insertion is crucial to minimize complications. The healthcare provider should carefully assess the patient's veins and choose an appropriate site.

  4. Monitoring for potential complications: Constant monitoring of the IV site is essential to identify any signs of infection, infiltration, or phlebitis. Common signs to watch for include redness, swelling, pain, and warmth at the injection site.

  5. Regular infusion rate assessment: Healthcare providers should regularly monitor the infusion rate to prevent overhydration or clotting of the IV line. This is particularly important when administering certain medications or fluids that have specific infusion rate requirements.

  6. Proper IV catheter and tubing care: The IV catheter insertion site and tubing should be kept clean and free from contamination. The dressing around the catheter should be observed for any signs of loosening or wetness, which could indicate infection or dislodgment.

  7. Securement of the IV line: The IV line and catheter should be securely taped or anchored to prevent accidental dislodgment or infiltration.

  8. Checking for allergies and compatibility: Before administering IV fluids or medications, healthcare providers should review the patient's medical history and check for any known allergies or contraindications. It is crucial to ensure that the fluids and medications being administered are compatible and safe for the patient.

  9. Maintain aseptic technique during administration: During the administration of IV fluids or medications, healthcare providers should maintain aseptic technique by wearing gloves, using sterile equipment, and avoiding unnecessary touch or manipulation of the IV line.

  10. Proper disposal of used materials: All used IV equipment, including needles, tubing, and gloves, should be disposed of properly in designated biohazard containers to prevent accidental needle stick injuries and the spread of infections.

It is important for healthcare professionals to follow these precautions to ensure the safety and effectiveness of IV therapy and minimize the risk of complications.

A circuit contains two 1.5 volt batteries and a bulb with resistance of 3 ohms calculate the current?

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Asked by Wiki User

If the batteries are placed in series then your current would be 1 amp, if the batteries were in parallel then 0.5 amps.

Voltage is common in parallel and additive in series.

1.5v + 1.5v = 3v (series) / 3 ohms = 1amp

1.5v (parallel) / 3 ohms = 0.5amps

Current = Voltage divided by Resistance

What would b the effect on the circuit should the starter be taken out after the lamp is started?

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Asked by Wiki User

Once started the fluorescent tube no longer needs the starter. In fact starters are designed to electrically "remove" themselves from the circuit when the fluorescent tube is conducting.

What flows through a circuit and causes a magnetic field?

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Asked by Wiki User

An electric current flowing through a circuit causes a magnetic field. This is due to the movement of electric charges, usually electrons, in the circuit. The magnetic field produced is perpendicular to the direction of the current flow.

What are the two ways in which a circuit may be arranged?

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Asked by Wiki User

A circuit can be arranged in either a series or parallel configuration. In a series circuit, the components are connected in a single path, so the same current flows through each component. In a parallel circuit, the components are connected in multiple paths, allowing different currents to flow through each component.

What is a resistor whose value can varied over a range of value called?

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Asked by Wiki User

Variable resistor. The value of the variable resistor can be changed at any given moment.

Is food a conductor or insulator?

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Asked by Wiki User

Neither, really. Most foods are not good conductors, but do conduct somewhat because they tend to contain ions in solution.

What is the effect of changing the numbers of batteries in a circuit?

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Asked by Wiki User

Before we can attempt an answer to that question, we'll need to agree on the

meaning of the fuzzy, slippery phrase "amount of electricity". I'm going to interpret

that phrase to mean the current through the circuit.

If the batteries are connected in series, then more batteries produce more current

through the circuit.

If the batteries are connected in parallel, then the number of them has no effect

on the magnitude of current through the circuit. But whatever the current is, more

batteries will cause it to flow in the circuit for a longer time, before they run down.

What does the voltage rating of a capacitor mean?

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Asked by Wiki User

The voltage rating of a capacitor is the maximum amount of voltage that a capacitor can hold. Going above this rating can damage and destroy the capacitor.


Exceeding a capacitor's voltage rating can cause its dielectric to break down. A capacitor's voltage rating is generally expressed as a d.c. voltage so, if it is to be used with an a.c. system, it's necessary to know the peak value of the a.c. voltage, which is determined by dividing the a.c. (rms) voltage by 0.707.

What is a circuit switcher?

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Asked by Wiki User

Circuit Switching

Circuit switching is used for ordinary non-digital telephone systems. It allows communications equipment and circuits to be shared among users. Each user has sole access to a circuit (functionally equivalent to a pair of copper wires) during network use.

A circuit switching network is the one that establishes a dedicated circuit or channel between nodes and terminals before the user may communicate. Each circuit that is dedicated cannot be used by other callers until the circuit is released and a new connection is set up. Even if no actual communication is taking place in a dedicated circuit's channel, that channel still remains unavailable to other users. Any other channel that is available remains unconnected (set to "idle") until a new call appears.

Why is the main switch connected in series together with the rest of the circuits in the house?

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Asked by Wiki User

It is connected so that it can disconnect the entire power grid in the house with one switch. This switch is usually integrated into a circuit breaker. No matter how one looks at it, this switch must be made to withstand (and be able to switch) great currents (in excess of 16A) at relatively high voltages (120V/230V).

Special care must be taken during the design phase, as the switch will most likely have to suffer severe arcing as well as heating, during normal operation.

What is harmonics in electrical circuits?

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Asked by Wiki User

By simple definition, harmonics are any "non-linear" current or voltage in an electrical distribution system. An electrical harmonic shouldn't be thought of as an acoustic or vibrational harmonic, but simply as any electrical device that draws current un-proportionally to voltage. Harmonics are commonly produced by devices that rectify AC Voltages into a DC Voltages. Common harmonic producing devices are VFDs, lighting, and computers.

When do harmonics cause problems?Current Harmonics

These important bridge rectifier circuits produce current harmonics. Current harmonics do have an affect on the electrical equipment supplying harmonic current to the device (transformers, conductors). Current harmonics can cause issues with distribution equipment which has to handle the current from the utility transformer all the way down to the device, but generally don't affect other equipment connected to the electrical system. Harmonic currents can cause excessive heating to transformers. For electrical systems feeding single phase loads the third harmonic has gained attention in design consideration and transformer selection for causing the neutral conductor to draw excessive current.

Voltage Harmonics

Voltage harmonics can effect sensitive equipment throughout your facility. Voltage harmonics arise when current harmonics are able to create sags in the voltage supply. When any device draws current it creates a voltage dip which is required for current to flow. This voltage dip is visible with larger loads when turning on a hair dryer or a table saw and seeing the lights dim down. The amount of sag depends on many factors like transformer impedance wire size. Current harmonics create voltage harmonics, but the magnitude of the voltage harmonics depends on the "stiffness" of your electrical distribution's "system impedance."

An example to help understand current distortion verse voltage distortion is the common CFL light bulb. This low cost light bulb may have a 75% current THD (total harmonic distortion). This means that 75% of the current drawn by the bulb is considered "harmonic current". These light bulbs usually do not affect other devices in your home because even though the current drawn by the bridge circuit is rich in harmonic current, it creates very little sag in your home's voltage supply, and if you had a voltage analyzer attached you would probably see a voltage THD of well less than 1 percent.

Avoiding Harmonic Issues

If possible it is best to select equipment with a low current THD, and the result would be reduced voltage THD. If you are not able to purchase equipment with a low current THD there may be options available to you like adding line chokes or isolations transformers to reduce the harmonic currents. If you are unable to reduce current distortions and are having issues with the affects of voltage distortion there are options, such as tuned capacitor to supply harmonic current, or possibly redesigning your systems distribution to reduce system impedance.

Solutions for Mitigating Harmonics

There are many solutions to alleviating the affects of harmonics, below are some commonly applied solutions.

Reduce Current Harmonics

Add line chokes to harmonic producing equipment.

Add isolation transformer to harmonic producing equipment.

Use 12-pulse or 18-pulse rectifier circuits, instead of 6-pulse.

Reduce Voltage Harmonics

Add tuned capacitor banks to supply harmonic current, or change transformer size/impedance.


Isolate sensitive loads instead of mitigating harmonics.

What wire size is needed for 15 volt circuit?

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Asked by Wiki User

The wire size depends on how much current it will conduct.

What type of a circuit do flashlights use?

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Asked by Wiki User

A flashlight is a series circuit. The batteries positive end connects to the flashlights switch. The switch connects to the center pin of the light bulb. The bulb filament is connected to the center pin of the bulb and the outer metal shell of the bulb socket. The shell of the bulb socket is connected to the metal flashlight's body which returns to the negative end of the battery. Turn on the switch and you have light.

What is a latching circuit?

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Asked by Wiki User

A latching circuit is a circuit with two stable states, which one can think of as 1 and 0, thereby being able to store one bit of information. In circuit diagrams, these are represented by cross-coupled NOR or NAND logic gates.

Advantages of semiconductor diode over vacuum tubes?

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Asked by Wiki User

A semiconductor diode has these advantages over a vacuum tube:

  • smaller
  • cheaper
  • runs cooler
  • much more rugged
  • very long life
  • no heater, so needs no power supply to work
  • less electrically noisy
  • can be made part of an I.C.

What is the clip voltage?

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Asked by Wiki User

When V(gs) is less than V(t). The minimum external energy which is provided to V(gs) in order to cross v(t) is know as clip voltage.

Total opposition to current flow in an AC circuit?

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Asked by Wiki User

I oppose alternating current. Direct is the only way for me. That is 1 in opposition.

What is voltage level of ttl?

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Asked by Wiki User

Standard TTL (which stands for Transistor-Transistor Logic) circuits operate on a 5V power supply. The typical level for a logical "0" is between 0V and 0.8V, and the typical level for a logal "1" is somewhere between 2.2V and 5V. Typically, a value little lower than Vcc (power source voltage) is used; in case of a 5V supply, this is usually around 4.5V, but TTL devices are built to withstand full Vcc as input, just in case.