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What is the name given to devices whose resistance remains constant as current increases?
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What happens to the current as the resistor approches infinty?
Most resistors are linear, or 'ohmic', devices -which means that they obey Ohm's Law. So the ratio of voltage to current remains constant for variations in voltage. In other words, their resistance remains constant -providing their power rating isn't exceeded. So you can say that, providing the current increase doesn't cause their power rating to be exceeded, their resistance should remain the same. Resistors wouldn't be of much use if their resistance value changed whenever the current through them changed!
What changes occur in the total resistance of a circuit as additional resistances are added in parallel?
The total resistance of the circuit increases. hence the new resistance after adding the resistance will be new resistance = old resistance + added Resistance There is a small mistake in the question. The second word is 'changes' not 'charges'
What is the relationship of current and voltage in a resistive circuit?
The current through the circuit is directly proportional to the voltage across the circuit. The proportionality constant is 1/R, where 'R' is the total effective resistance of the circuit. C = V / R V = C R R = V / C
Do all electrical and electronic circuits obeys ohms law?
Ohm's law is always true. That's what makes it a law. What trips people up is that resistance is not constant. The law states that voltage is current times resistance. That is true, no matter what. The calculations can become complex, because resistance is not constant.Another AnswerProbably not. But it really depends on the shape of the characteristic curve for its application (e.g. diode). Despite being fundamental, Ohm's Law is one of the least understood so-called 'laws' in electrical engineering. It applies in so few cases, in fact, that many engineers and physicists argue that it should not be called a 'law' at all!Ohm's Law is not a universal law, and onlyapplies when the ratio of voltage to current is constant for variations in voltage. This only applies to linear or 'ohmic' devices. Most electronic devices are non-linear or 'non-ohmic' and these include vacuum tubes and solid-state devices, etc. Even some pure metals, such as tungsten, are non-linear -so incandescent lamps, for example, do not obey Ohm's Law.Ohm's Law only applies to conductors and circuit devices that produce a straight-line graph when current is plotted against variations in voltage. If the resulting graph is curved, then Ohm's Law doesn't apply. Period!Think about it: if you, say, double the voltage for a curved graph line, the resulting current doesn't double in value -so it can't be obeying Ohm's Law (which states that 'current is proportional to voltage').Of course, some vacuum tubes and solid-state devices have voltage/current characteristic curves that are partly-curved and partly-straight -in these cases Ohm's Law applies only the the straight-line parts of those characteristic curves, but not to the curved parts. Some devices have 'negative' curves, in which current increases when the applied voltage decreases -clearly these do not obey Ohm's Law, either!Having said that, for non-linear devices, you can use the ratio of voltage to current (= resistance) to find out what the resistance happens to be for any particular ratio of voltage to current -i.e. at a specific point along their graph line.
Is it true that ohm's law states that current is directly proportional to the voltage and inversely proportional to the resistance?
No. Ohms Law states the relationship between voltage, current, and resistance, not between voltage, current, and charge. (Volts = Amps * Ohms)Another AnswerOhm's Law is not a universal law; in fact, it barely qualifies as a scientific law at all, because it only applies in a very limited number of controlled circumstances. Put simply, Ohm's Law states that 'the current in a conductor is directly proportional to the potential difference across that conductor, providing all physical conditions, such as temperature, remain constant'. So, as you can see, Ohm's Law only states the relationship between current and voltage.Ohm's Law, then, ONLY applies when the ratio of voltage to current is constant for variations in voltage. Put another way, Ohm's Law only applies when the resulting graph of voltage to resistance is a straight line.Unfortunately, this is rarely the case. For example, if you were to increase the voltage across a conductor, such as tungsten, the resulting increase in current would cause that conductor's temperature to rise, thus invalidating Ohm's Law, and producing a curved graph, rather than a straight-line graph.So, Ohm's Law does NOT apply to most conductors, or to most electronic devices, such as diodes etc., other than for the straight-line parts of their characteristic curves.Ohm's Law is frequently, but mistakenly, expressed by the equation, R = U/I (where R = resistance, U = voltage, and I = current). This equation, however, is derived from the definition of the ohm and NOT from Ohm's Law.
What happens to the current as the resistor approches infinty?
Most resistors are linear, or 'ohmic', devices -which means that they obey Ohm's Law. So the ratio of voltage to current remains constant for variations in voltage. In other words, their resistance remains constant -providing their power rating isn't exceeded. So you can say that, providing the current increase doesn't cause their power rating to be exceeded, their resistance should remain the same. Resistors wouldn't be of much use if their resistance value changed whenever the current through them changed!
Why the resistant in ohmic devices is constant and in non ohmic not constant?
the resistant in ohmic devices is constant because it depend on temperature ..and temperature is constant independent of polarity of potential difference...btin non ohmic the tempt increase with voltage which increase due to the heat increase beacue of power dispition....collision of electrons increases find more resistenc for passing so resistence increases
What is an reactance?
it is a internal resistance of the devices like as capacitor and inductorCommentAs 'resistance' has a very specific meaning, I suggest that the above answer should read: 'It is the opposition of devices like capacitors and inductors (to the flow of current).'
How does connecting devices in parallel affect the electric current in a circuit?
it doesn't, the one with the highest resistance does
How induction motor heatup?
The temperature of all electrical devices will result as a consequence of the current passing through its conductors. In the case of motors, further temperature increases are brought about as a result of bearing friction, windage (air resistance), and eddy-current/hysteresis losses in the rotor and stator.
What law relates to voltage amperage and resistance?
Current is directly proportional to the applied voltage and inversely proportional to the resistance in the circuit. Short form, resistance goes up current goes down, resistance goes down current goes down.This answer is incorrect.First of all, resistance is not affected by a change in voltage or in current. Resistance is only affected by the length, cross-sectional area, and resistivity of the conductor (and, indirectly, by temperature which affects resistivity).Ohm's Law makes no mention of resistance. It simply states that the current flowing in a circuit is proportional to the applied voltage, providing external factors, such as temperature, remain constant.Since current is proportional to voltage, it must be equal to a constant times voltage. This constant is called conductance, which is the reciprocal of resistance, so the so-called 'Ohm's Law formula' is usually shown as I = V/R. But it's important to remember that the resistance, R, is a constant and does not change if V or I changes.
When voltage increases what happens to current?
Ohm's law states that "The current is directly proportional to the applied EMF (voltage) and inversely proportional to the resistance in the circuit."AnswerIf the voltage across a circuit increases, then the current will increase too. If the ratio of voltage to current is constant for variations in voltage, then the circuit is described as being 'linear' and is obeying Ohm's Law; if the ratio of voltage to current changes (as it would, for example, with tungsten) for variations in voltage, then the circuit is described as being 'non-linear', and is not obeying Ohm's Law. This is because Ohm's Law is not universal, and only applies to certain materials; in fact, most materials and electronic devices do not obey Ohm's Law.
What are devices that obey ohm's law called?
All devices obey Ohm's law. That is why its called a law.The misunderstanding is that Ohm's law does not say that resistance is constant - it says that resistance is voltage divided by current.Very few devices actually have constant resistance. Even the resistor is not constant, due to thermal properties.AnswerI beg to differ with the previous answer. The term you are looking for is a 'linear' device. 'Non-linear' devices, on the other hand, include some semiconducting devices, such as diodes, but also includes certain metals such as tungsten. What it basically comes down to is that if there isn't a linear relationship between current and voltage, then the device is not obeying Ohm's Law!Ohm's Law simply states that, 'providing external factors such as temperature remain constant, then the current flowing in a circuit is proportional to the applied voltage'. It most definitely doesn't say that 'resistance is voltage divided by current'!! In fact, it doesn't even mention resistance!Ohm's Law is not an equation, despite it often being taught as such in high schools by teachers who should know better, but who misinterpret the Law by over-simplifying it (some high school teachers shouldn't even be teaching science, as they are responsible for many other misconceptions too!).For current to be proportional to voltage, there must be a constant of proportionality. This is called conductance, expressed in siemens. However, it is more usual to use the reciprocal of conductance, which is resistance, expressed in ohms, that is: U = R I, where Ris a constant.In other words, Ohm's Law is only true providing resistance is constant. So an incandescent lamp, for example, which uses the non-linear metal tungsten, as a filament, does not obey Ohm's Law. This is because its temperature increases significantly as the voltage across it is increased and, so, the resulting current does not increase proportionally with that voltage. Even 'linear' devices become 'non-linear' at some point, usually at extreme temperatures, once again reinforcing the fact that Ohm's Law only applies providing the temperature doesn't affect resistance.To put it another way, if there isn't a straight line relationship between current and voltage, then the device ain't obeying Ohm's Law!However, for any given voltage, you can certainly use the equation R = U/I to determine what the resistance happens to be at that particular voltage-but that isn't what Ohm's Law says. Ohm's Law isn't about a what happens at a particular voltage! It's about the current remaining proportional to the current over a wide range of voltage variation.
What is the Difference between voltage controlled device and current controlled device?
The difference between a current control device and voltage controlled device is that for current controlled device, the current is constant and the voltage is variable while for a voltage controlled device, the voltage is constant and the current is variable.
How do you calculate absolute maximum current?
The absolute maximum current is used as part of a rating system, particularly for electronic components. It is a figure that a manufacturer will quote to indicate how much current can pass into or out of a device or a specific connection on the device. Exceeding that limit is likely to damage the device. The absolute maximum value is one that should never be exceeded but it is also normally higher than the maximum recommended current. The value is often measured during tests rather than calculated. The question might refer to the amount of current that might be drawn by a device. In this instance, to calculate the absolute maximum current that a device or component might draw there are two pieces of information needed. The first is the voltage that is applied to the device. The second is the lowest possible resistance that the device can have. Devices such as resistors, filament lamps and heaters have a constant resistance but active devices such as amplifiers, computers etc. can change resistance as they operate. It can be hard to find the resistance with some devices but once it has been established, Ohm's Law can be used to calculate the maximum current using the equation current = Volts divided by resistance. It is normally much easier to measure the current using an ammeter rather than trying to find the lowest resistance.
What is a posistor?
A Posistor is actually Murata's "name brand" for a device called a Positive Coefficient Thermistor. Used in many in-rush current control circuits, a positive coefficient thermistor is a resistor that starts with a relatively low resistance value at room temperature (25C) then, when heated from current flowing through it, its value quickly rises to a very high resistance.One very common use of this device is to control the current flow through a CRT degaussing coil on picture-tube style (CRT) televisions and monitors.These devices come in either positive coefficient thermal values (PTC) (eg: resistance increases as temperature / current increases) or negative coefficient values (NTC) (eg: resistance decreases as temperature / current increases).Manufacturers include Nichicon, Murata, Vishay and a myriad of discrete device companies.(Eric Peterson, Dunedin FL)
Which current is used for electronic devices?
It depends on the amount of resistance, or load, the device is on the circuit. Do you have a particular device you're asking about?
