0
What emits light when the current flows from the anode to the cathode?
Wiki User
∙ 12y ago
lioght
Wiki User
∙ 12y ago
Add your answer:
Earn +20 pts
What are the parts in a diode?
That depends on the diode, however I will talk about a very basic one. Simple version: One side is called the anode, the other is the cathode. Current only flows from the anode to toward the cathode. It is blocked from traveling in the other direction. Less simple version: I am including this since you asked about the parts "in" a diode and not the parts "of" a diode. Diodes are semiconductor devices and are constructed with two pieces of semiconductor material (silicon, germanium, etc), one of which has been designed with extra electrons in it (cathode side) and one with extra spots for electrons to occupy (anode side) . Remember current flowing in one direction means electrons are traveling in the opposite direction. Now, if you apply enough positive voltage to the cathode, current will flow to the anode, but it will damage the diode if it is not designed to handle it. Some diodes are even designed to be used this way (look up zener diodes). To really understand the physics of what is happening in these materials, you need some knowledge of quantum mechanics (not joking) but that is beyond this question. Hope you got what you needed.
How is the plus and minus voltage sign for resistance voltage drops for battery voltages and currents be determined?
The plus and minus voltage sign for resistance voltage, drops for battery voltages, and drops for currents is determined by convention. You can use whatever method you want - so long as your use is consistent, your analytical results will be correct for you.The commonly accepted convention, however, is best. This way, other people reviewing your results will not be confused unless, of course, they use an atypical convention.Electric current flow is electron flow. The battery terminal marked "negative", or the cathode, is the source of electrons, and those electrons are drawn to, and flow towards, the "positive" terminal, or anode.Consider a simple circuit, consisting of a battery in series with a resistor. Draw the battery on the left, with the anode up. Draw the resistor on the right. Connect the anode to the top of the resistor, and the cathode to the bottom of the circuit. (Actually, this is also a parallel circuit, with the battery in parallel with the resistor. It depends on how you see it, because this is a simple circuit.)Current flows out of the bottom (cathode, negative) battery terminal, into the bottom of the resistor, up through the resistor to its top, over to the left, and into the top (anode, positive) battery terminal, and down through the battery, completing the circuit at the cathode. This is counter-clockwise, if you have drawn the circuit as stated.If you place a voltmeter across the battery, you will see that the anode (top) is more positive than the cathode. If you place a voltmeter across the resistor, you will see that the top is more positive than the bottom. It does not matter if you measure across the battery or the resistor, the voltage will be the same. If you place the voltmeter across the wire on the bottom, or across the wire on the top, you will see that the voltage is zero.With the preliminaries out of the way, now to the convention.Current flow is counter-clockwise, from cathode to anode. If you were to draw a current arrow, you could draw it counter-clockwise, down through the battery and up through the resistor. You would label the first point that the current encounters (the bottom of the resistor) as negative, or minus. As the current goes through the resistor, it becomes more positive, so you would label the top of the resistor positive, or plus. Go over to the anode. That is also plus. The current is made more negative due to the battary being a source, rather than a load, so the cathode is minus.These pluses and minuses are relative to each other, and they are also relative to some common reference point, said point by convention being the cathode. In this simple circuit, there is only one point that has any voltage different than the cathode, and that is the anode, so this distinction might be vague.Consider then, the case where the resistor is actually two resistors in series. Again, the bottom resistor starts minus on its connection to the cathode, it becomes more positive as the current goes up, making the top of the bottom resistor plus. The bottom of the top resistor is minus, because current is flowing into it, and it becomes more positive as the current goes up, with the top of the top resistor plus.When you measure voltage across an element, you see the voltage for that element. If, instead, you measure the voltage relative to the common reference point, and there is more than one element between the voltmeter's leads, you add up the voltage rises or drops to figure out what to expect. In fact, this is the basis for Kirchoff's voltage law - that the signed sum of the voltage drops around a series circuit always adds up to zero.So, this preliminary convention is that current flow leaves the minus terminal of a voltage or current source, and enters the minus terminal of a voltage or current load. It then enters the plus terminal of a voltage or current source, and leaves the plus terminal of a voltage or current load.Now, to confuse you, another convention states that current flows from plus to minus, not from minus to plus. This means that current leaves the plus terminal of a source, and enters the plus terminal of a load, and it enters the minus terminal of a source and leaves the minus terminal of a load.It does not really matter which convention you use. The positions of the plus and minus signs will be the same - its just that the current arrow will point in the opposite direction - in this example, clockwise instead of counter-clockwise. What is important is to be consistent in your use of the plus or minus sign as the current enters and leaves a source or a load.The convention of current flow is arbitrary. So long as you are consistent in your application, you will get the correct results.It is generally accepted that current flow is electron flow, which means that current flows from the negative side of a voltage or current source towards the positive side.Often, however, current is considered to flow from positive to negative. While this makes perception in circuit analysis more straightforward, it does not change the analytical results.
Is the amount of current that flows in the wire of electric circuit the same as the current that flows in the filament of the light connected in that circuit?
yes
What is LED and its construction and working?
LED is an abbreviation for light-emitting diode. An LED consists of a chip of semiconducting material doped with impurities to create a p-n junction. As in other diodes, current flows easily from the p-side, or anode, to the n-side, or cathode, but not in the reverse direction. Charge-carriers - electrons and holes - flow into the junction from electrodes with different voltages. When an electron meets a hole, it falls into a lower energy level, and releases energy in the form of a photon. For more information, see related links, below.
True or false The total current that flows through a circuit is the same as the current that flows through each individual parallel sub-circuit?
True
Why is galvanometer used when you know that electric current travels from cathode to anode of the battery?
I think that you talk about the usage of galvanometer in photoelectric emission experiment. Right? The main purpose of using a galvanometer is to know about whether current flows or not and also the direction in which current flows. Moreover current flows right from anode to cathode and electrons do flow from cathode to anode within the discharge tube.
What is the direction of current in picture tube of TV?
A cathode ray tube (CRT) emits light when electrons strike the front of the glass tube that is covered in a phosphor coating. The front of the tube is the anode of the tube. The electrons are fired from the rear of the tube by an electrode called the cathode. The electrons are formed into a beam or ray, hence the name of cathode ray tube. Although the electrons travel from the rear of the tube to the front, or from the cathode to the anode, conventional current actually flows the opposite direction. So, the current, as measured in amps will flow from the anode to the cathode.
Why current flows from cathode to anode in the internal circuit of a simple cell?
generally electrons will move towards positive charge and conventionally current flows in opposite direction to it
Which side of diode is anode and which is cathode on the diode in a schematic?
The anode is the arrow shaped end, while the cathode is the bar shaped end. You can remember this by recalling that current flows from anode to cathode in an ordinary diode; well, that is, if you use the trick of assuming that current is hole flow, rather than electron flow, a useful and common convention. The exception, of course, is the zener diode, where current flows in both directions, but at different potentials. In this case, there are two 45 degree angled bars at the end of the cathode symbol, and the normal configuration of current flow is cathode to anode, backwards with respect to an ordinary diode.
How does tha current flows in the circuit?
Most people agree that current flows from the negative (cathode) terminal of the voltage source, through the load, and back to the positive (anode) terminal of the voltage source. This is because it is accepted that current is a flow of electrons. However, most analyses techniques use the convention that current flows from anode to cathode. It is simply a convention. So long as you are consistent in your usage of signs, you will be OK.
In the electrolytic cell electron flows from?
Electron flow is from anode (+) to cathode (-)
What are anodes?
negative electrode
What is batterty?
A battery is a device that stores electric charge by chemical means. Every battery has a anode and a cathode, which corresponds to the positive and negative terminals. The current always flows from the positive (anode) to the negative (cathode) terminal. Because it's a chemical process, batteries always discharge and charge much slower than capacitors, but on the upside always have much more capacity than capacitors.
What is the cathode in an electrochemical cell?
The electrode at which a reduction reaction occurs.PhysicsA cathode is the element of an electron tube from which electrons flow. Back in the day, current was thought to be positive, but we understand things differently now. In the "old school" version, the cathode was the element into which positive charges flowed. But that's usually not what is taught for the simple reason that it's a classical physics approach and isn't at all as useful as the idea that the cathode is the element from which electrons leave to go to the plate.In a two-element tube, the cathode has a compliment called the anode, or plate. Electrons flow from the cathode to the anode. Not the other way. There are tubes with three, four, and more elements, but they have these two basic elements.ChemistryThe cathode is the electrode of a polarized electrical device, such as a galvanic cell, out of which positive electric current flows. In a battery like the one in a vehicle, the positive terminal is the cathode. The car battery, which is a lead-acid battery, also has an electrode that is the compliment to the cathode: the anode. It's the negative terminal of the battery, and positive electric current flows into this electrode.The Wikipedia article on the cathode covers both the chemistry application of the term as well as the physics application, and a link is provided.
Why does a diode not conduct in reverse bias?
A diode cannot conduct in reverse bias because of the way it was made. If the question is asking about a thermionic vacuum tube diode, the electrons produced by the heated cathode of the tube can only move in one direction: from the cathode to the anode - but only for as long as the anode is positively charged. The reason is that, if the anode is made to be positively-charged, it ATTRACTS electrons - which are negatively charged - from the cathode, so a current flows from cathode to anode in the "normal" biased direction because of the physical fact that UNLIKE CHARGES ATTRACT ONE ANOTHER. If the anode is made to be negatively charged, the electrons won't go to it because of the physical fact that LIKE CHARGES REPEL ONE ANOTHER, so no electrical current can flow from the cathode to a negatively charged anode. (In fact no electrical current can ever flow from a negative anode to the cathode for an entirely different reason: no anode of any normal thermionic vacuum tube was ever designed and made to "produce" electrons in the way that a heated cathode produces them!) To be able to "produce" electrons and let them fly to the positively charged anode, the cathode must be able to receive some more electrons to replace all the ones that have left the space around the cathode. That "supply of more electrons" is called an electric current. That current does not come from nowhere - it has to comes from a source, such as a battery or a generator - and the electrons which reach the anode must then be conducted back to the battery or a generator so that they complete a full electrical circuit by traveling along the wires which connect the source to the diode. Similarly, because of the way it was made, a semiconductor diode behaves in just the same way as a vacuum tube diode: electrons can flow from the negative end to the positive end of the semiconductor diode but not the other way around. The actual reason why a semiconductor diode works like that is very much more complicated to explain than for a vacuum tube diode. Put very simply, a semiconductor diode has the kind of materials inside it that will only allow electrons to flow one way. If a voltage is applied to the diode the wrong way round (called reverse bias) practically no current can flow through the diode.
Why diode does not conduct in reverse bias?
A diode cannot conduct in reverse bias because of the way it was made. If the question is asking about a thermionic vacuum tube diode, the electrons produced by the heated cathode of the tube can only move in one direction: from the cathode to the anode - but only for as long as the anode is positively charged. The reason is that, if the anode is made to be positively-charged, it ATTRACTS electrons - which are negatively charged - from the cathode, so a current flows from cathode to anode in the "normal" biased direction because of the physical fact that UNLIKE CHARGES ATTRACT ONE ANOTHER. If the anode is made to be negatively charged, the electrons won't go to it because of the physical fact that LIKE CHARGES REPEL ONE ANOTHER, so no electrical current can flow from the cathode to a negatively charged anode. (In fact no electrical current can ever flow from a negative anode to the cathode for an entirely different reason: no anode of any normal thermionic vacuum tube was ever designed and made to "produce" electrons in the way that a heated cathode produces them!) To be able to "produce" electrons and let them fly to the positively charged anode, the cathode must be able to receive some more electrons to replace all the ones that have left the space around the cathode. That "supply of more electrons" is called an electric current. That current does not come from nowhere - it has to comes from a source, such as a battery or a generator - and the electrons which reach the anode must then be conducted back to the battery or a generator so that they complete a full electrical circuit by traveling along the wires which connect the source to the diode. Similarly, because of the way it was made, a semiconductor diode behaves in just the same way as a vacuum tube diode: electrons can flow from the negative end to the positive end of the semiconductor diode but not the other way around. The actual reason why a semiconductor diode works like that is very much more complicated to explain than for a vacuum tube diode. Put very simply, a semiconductor diode has the kind of materials inside it that will only allow electrons to flow one way. If a voltage is applied to the diode the wrong way round (called reverse bias) practically no current can flow through the diode.
When electric circuit is closed no current flow through it IS the statement is correct?
yes... this is possible if a diode i connected in reverse bias with a battery and a resistor for example. A diode in reverse bias means its anode will be connected to positive terminal of the battery and its cathode to the negative terminal of the battery. In such a case, minimal current flows through the circuit which can be neglected.
