0
Circuits
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.
1,646 Questions
A circuit works because it allows electrical current to flow continuously, completing a loop from the power source through the components and back. This flow of current enables the components in the circuit to perform their intended functions, such as lighting up a bulb or powering a device. The components in the circuit, like resistors, capacitors, and transistors, interact in specific ways to control the flow of electricity and perform desired tasks.
What does it mean when you say that energy is lost in a resistor?
When we say that energy is lost in a resistor, it really means that electrical energy has bee transformed into other forms of energy. These other forms of energy do not easily get changed back into electrical energy.
Why is the threshold voltage for nerve lower than the threshold voltage for muscles?
The threshold voltage for nerves is lower than for muscles because nerves rely on smaller ion channels that open more easily, allowing for faster nerve conduction. In contrast, muscle cells have larger ion channels that require a higher voltage to open, resulting in a higher threshold voltage for muscle activation.
A zero reading on an ohmmeter means the circuit or component is open is this true or false?
This is false. A zero reading is what you get when you press the probes of the
meter together with nothing between them, to make sure the meter is working.
That's about as closed as the circuit under test can get.
What might happen to a bulb if you added too many extra batteries to the circuit?
If you added more batteries in parallel, then the bulb would shine for a long time.
If you added more batteries in series, then the bulb would burn very brightly for a short time and then 'burn out'.
What is a type of pressure that drives electrical charges through a circuit?
conductor is a material through which electric current flows easily.
Electric charge is a basic feature of certain particles of matter that causes them to attract or repel other charged particles.
Electric circuit is the path that an electric current follows.
Electric current is the flow of electric charges.
Electric field is the influence a charged body has on the space around it that causes other charged bodies in that space to experience electric forces.
Electrode is a piece of metal or other conductor through which current enters or leaves an electric device.
Electromagnetism is a basic force in the universe that involves both electricity and magnetism.
Electron is a subatomic particle with a negative electric charge.
Insulator is a material that opposes the flow of electric current.
Ion is an atom or group of atoms that has either gained or lost electrons, and so has an electric charge.
Kilowatt-hour is the amount of electric energy a 1,000-watt device uses in one hour.
Neutron is a subatomic particle that has no electric charge.
Ohm is the unit used to measure a material's resistance to the flow of electric current.
Proton is a subatomic particle with a positive electric charge.
Resistance is a material's opposition to the flow of electric current.
Static electricity is electric charge that is not moving.
Voltage is a type of "pressure" that drives electric charges through a circuit.
Watt is the unit used to measure the rate of energy consumption, including electric energy. Current_Electricity">Current Electricity Electric current is the movement or flow of electric charges. A charge can be either positive or negative. The protons that make up part of the nucleus of every atom have a positive electric charge. The electrons that surround the nucleus have a negative charge. An electric current can consist of positive, negative, or both types of charges.
The American statesman and scientist Benjamin Franklin originated the idea that electric current flows from positive to negative. But other scientists later proved that electric current actually flows in the opposite direction--from negative to positive.
Franklin's idea also fails to describe the way electric current flows through metals. Each atom of a metal wire has at least one electron that is not held so closely by the nucleus as the others are. Such loosely held electrons can move freely through the metal. But the nucleus cannot move through the wire. Thus, current flowing through a metal wire consists of free electrons.
Conductors and insulators. Electric current flows most easily through substances called conductors. The number of free electrons in a substance determines how well it conducts current. Such metals as aluminium, copper, silver, and gold are good conductors because they have at least one free electron per atom. Some metals, such as lead and tin, are poorer conductors than other metals because they have less than one free electron per atom. Poor conductors resist the flow of electric current more than good conductors do. Resistance changes electric energy into heat. Engineers use units called ohms to measure resistance (see OHM).
Substances with no free electrons, such as glass, mica, and rubber, do not normally conduct electric current. They are called insulators. Some substances, including germanium and silicon, are neither good conductors nor insulators. They are called semiconductors (see SEMICONDUCTOR).
To produce an electric current, some type of nonelectric energy must be converted into an electromotive force (emf). For example, a battery creates an emf by changing chemical energy into electrical potential energy. Thus, a battery has a potential difference (difference in potential energy) between its ends that causes electrons to flow in a conductor. Emf is measured in units called volts. An emf of one volt, when connected to a conductor with a resistance of one ohm, causes 6,241,500,000,000,000,000 electrons to flow past a point in the conductor in one second. This amount of electric current is called one ampere. See VOLT; AMPERE.
Direct and alternating current. An electric current is either direct or alternating. Direct current (DC) always flows in the same direction. It is produced by batteries and DC generators. Alternating current (AC) regularly reverses its direction of flow. It is produced by AC generators. Nearly all homes and other buildings use AC.
Each time AC completes two changes of direction, it goes through one cycle. The number of cycles per second is called the frequency of the AC. Frequency is measured in units called hertz. Power is generated at 50 hertz in some countries and 60 hertz in others.
Direct current operates car electric systems, locomotives, and some types of motors used in industry. Radios, television sets, and other electronic devices use AC, but they also need DC to operate their internal circuits. Devices called rectifiers easily change AC into DC. DC is also necessary in order to charge storage batteries.
Alternating current has several advantages over DC. Its major advantage is that power stations can transmit it easily and efficiently. Electric current loses the least amount of energy when travelling at high voltages. But these high voltages are not safe to use in homes. Devices called transformers can easily increase or decrease AC voltage.
A conductor can carry more than one alternating current at a time. A current consisting of two more individual alternating currents is known as a polyphase current. One common kind of polyphase current is three-phase current, which consists of three individual alternating currents.
Ensure the ammeter is set to the correct range for the expected current level to avoid damaging the meter. Connect the ammeter in series in the circuit to measure the current flowing through the circuit accurately. Always disconnect power before connecting or disconnecting the ammeter to prevent electrical hazards.
Can you still use series circuits in the future?
Yes, series circuits can still be used in the future for specific applications where you need the same current flowing through all components. They are commonly used in simple electronic devices, lighting systems, and some types of sensors. However, parallel circuits are more common and versatile due to their ability to power multiple components independently.
Why is a graph of voltage against current for a filament bulb curved?
Because as current increases, heat increases and therefore resistance increases. Since resistance is the gradient of the graph, the gradient will increase and therefore the graph will curve. (The filament in the bulb is an non-ohmic conductor; its resistance is only constant at a constant temperature.)
Another Answer
Incandescent lamp filaments are manufactured from tungsten. Tungsten is classified as 'non-ohmic' or 'non-linear', which means that (in common with most materials, in fact) it does not obey Ohm's Law. For a material to obey Ohm's Law, the ratio of voltage to current (i.e. its resistance) must remain constant for variations in voltage -as you have discovered, tungsten doesn't do this, producing a curve, rather than a linear, graph. As the original answer indicates, the temperature coefficient of resistance of tungsten in such that, as it gets warmer, its resistance increases.
Those few materials that do obey Ohm's Law are called 'ohmic' or 'linear' materials.
List 5 different ways magnets are used in every day life?
- Refrigerator magnets hold up notes and photos.
- Magnetic clasps are used in jewelry for easy fastening.
- Magnetic door latches keep doors closed.
- Magnetic compasses help with navigation.
- Magnetic closures on bags and purses keep items secure.
How does energy flow s through a electromagnetic circuit?
In an electromagnetic circuit, energy flows from a power source through the circuit components such as resistors, capacitors, and inductors. The energy is transferred through the circuit as electrical currents and magnetic fields, with some energy converted into other forms such as heat in resistors or stored in capacitors and inductors. Ultimately, the energy is dissipated or utilized to perform work within the circuit.
Why emitter bias circuit is called self bias?
The emitter bias circuit is called self-bias because the bias voltage across the emitter-resistor is based on the transistor's own characteristics. The bias voltage adjusts itself based on the varying collector current to stabilize the operating point of the transistor. It is a self-adjusting mechanism that helps maintain a stable bias point for the transistor.
What happen to voltage sensitivity if current sensitivity is increase of agalvanometer?
If current sensitivity of a galvanometer is increased, the voltage sensitivity remains the same. Voltage sensitivity depends on the resistance of the galvanometer coil, while current sensitivity depends on the number of turns in the coil. Therefore, changing current sensitivity does not affect voltage sensitivity.
The more voltage that is required to break down an insulator the greater its?
dielectric strength. Dielectric strength refers to the maximum electric field that a material can withstand without breaking down and allowing current to flow through it. Materials with higher dielectric strength are better insulators and can withstand higher voltages.
What is the units for the short circuit current?
The unit for short circuit current is typically measured in amperes (A) or kiloamperes (kA). It represents the maximum current that can flow in a circuit under a short circuit condition.
This question looks like one that has been asked by a high-school teacher with very little knowledge of electrical science, and who doesn't realise that the resistance of a lamp changes appreciable between when it is cold and when it is hot! (Either that, or he is being devious!)
So, as stated, this question is not straightforward, because incandescent lamps that operate at their rated voltage and power have a 'hot' resistance that is around 15 - 20 times their resistance when cold. Lamps in series are not subject to their rated voltage and, so, their resistance will be relatively low in comparison. So, what the question comes down to is whether the combined (high) resistance of lamps in parallel (i.e. half the resistance of one of the lamps) higher or lower than the combined resistance (low) of the same lamps connected in series (twice that of one of the lamps)? You could find this out experimentally, but I'd be inclined to believe that the two lamps connected in parallel are more likely to have the higher resistance and, therefore, the cell supplying them would last longer -in other words, opposite to that in your question!
Now, if you simply used two resistors (whose resistance doesn't change appreciably with temperature) then the two connected in series would definitely have a higher resistance (twice) than if they were connected in parallel (half), and they would draw less current and the cell would last longer.
The transfer characteristics of a JFET with external bias?
(i) Drain current decreases with the increase in negative gate-source bias
(ii) Drain current, ID = IDSS when VGS = 0
(iii)Drain current, ID = 0 when VGS = VD The transfer characteristic follows equation (9.1)
The transfer characteristic can also be derived from the drain characteristic by noting values of drain current, ID corresponding to various values of gate-source voltage, VGS for a constant drain-source voltage and plotting them.
It may be noted that a P-channel JFET operates in the same way and have the similar characteristics as an N-channel JFET except that channel carriers are holes instead of electrons and the polarities of VGS and VDSare reversed.
Why is an inductor called a choke?
An inductor is called a choke because it "chokes" or limits the flow of alternating current (AC) while allowing direct current (DC) to pass through. It acts as a choke to high-frequency signals, effectively blocking them while allowing DC or low-frequency signals to pass.
Which branch in a parallel circuit has the least amount of current flow?
In a parallel circuit, each branch has the same voltage but different current flows. The branch with the highest resistance will have the least amount of current flow, as current follows the path of least resistance.
The branch in a parallel circuit with the what will have the least amount of current flow?
The branch with the highest resistance will have the least amount of current flow in a parallel circuit. This is because current follows the path of least resistance, so more current will flow through branches with lower resistance.
What does a motor do to help the circuit from working?
A motor converts electrical energy into mechanical energy to perform a specific task, such as spinning a fan or moving machinery. It can draw a significant amount of current, which may affect other components in the circuit if it is not properly sized or protected. Adding safeguards like fuses or circuit breakers can help prevent damage to the circuit caused by the motor.
If two bulbs in a series circuit are equally bright then they transfer energy at different rates?
Whether or not they're in series is an irrelevant detail. If the two bulbs are equally
bright, it means that they're dissipating energy at the same rate. They can dissipate
energy at the same or at different rates whether they're in series or parallel circuits.
It only depends on the characteristics of the bulbs.
When current increases in an ac circuit what roll dose inductance play?
Inductance has no effect on the total current ... effective, RMS, amplitude, etc. ...
in an AC circuit. It only affects the phase difference (angle) between the voltage
wiggles and the current wiggles.
Describe how a meter would be connected in a circuit too measure the voltage at a light bulb?
When connecting a volt meter to a light bulb to measure the voltage of the light bulb, run a third wire from where the wire enters the bulb to one terminal of the voltmeter and a fourth wire from the other side of the bulb to the other terminal of the voltmeter.
What are the circuit effects due to a short circuit or open circuit?
It would depend on the circuit diagram. In some cases, the circuit would be incomplete (simplest case is a battery with a wire attached to just one terminal).
Parallel branches that have a connection to the battery without going through other branches are independent of each other. Say you have two parallel branches and a battery. If you short circuit one of the branches, the other branch will not be affected but the battery will be (current through the battery would decrease because taking out a parallel branch increases resistance).
In short, it would depend on the circuit diagram. Note that for a nanosecond, there would be current in an open circuit, but after this brief time there would be no current flow in the segment of the circuit that has been shorted.
