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As we know that skin effect occures in ac system.skin effect dependes on frequncy.In case of dc syastem frequncy is zero.So skin effect for conductor is not applicable for dc.
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Why are AC and DC resistance different?
An AC current tends to flow towards the surface of a conductor due to a phenomenon called the 'skin effect', which acts to reduce the effective cross-sectional area of that conductor.Since resistance is directly-proportional to the cross-sectional area of a conductor, the conductor's resistance to an AC current is, therefore, higher than its resistance to a DC current (which distributes itself across the full cross-sectional area). We call this elevated value of resistance, AC resistance.The skin effect increases with frequency to such an extent that, at radio frequencies, there is little point in using solid conductors and tubes are used instead. At mains' frequencies (50/60 Hz), however, the skin effect is moderate and, so, the value of a conductor's AC resistance is only slightly elevated compared to its true resistance.It's important not to confuse the term 'AC resistance' with 'reactance', which is a function of a conductor's inductance and/or capacitance, and the frequency of the supply.
Why we should have difference between dc and ac resistance?
Resistance is inversely-proportional to the cross-sectional area of a conductor. When a d.c. current flows, the charge carriers distribute themselves across the whole of the conductor's cross-section. When a.c. current flows, due to something called the 'skin effect', the charge carriers tend to flow towards the surface of the conductor -thus reducing the effective cross-sectional area of the conductor. So, the resistance to a.c. is higher than the resistance to d.c. At mains' frequencies (50/60 Hz), the 'skin effect' is relatively low, but the effect increases significantly with an increase in frequency. So the difference between 'd.c. resistance' and 'a.c. resistance' increases as the frequency increases.
What kind of current flows in the armature conductor of a dc generator?
pogi current flow in the armature conductor
Does the resistance depend on the frequency?
Yes. The resistance does depend on frequency. The reason is 'skin effect'. When an alternating current is passed through a conductor only a small portion of the conductor, usually called the skin depth carries the current. The value of skin depth is inversely proportional to frequency. As the frequency is increased, the skin depth decreases. But the value of ac resistance is directly proportional to frequency, or in other words, inversely proportional to skin depth. Thus, at higher frequencies, ac resistance is higher. This is the reason why we multiply the dc resistance by an empirical value 1.2 or 1.3 to calculate its ac equivalent.
Current in a solid conductor is a result of movement in?
the current is actually a result of many factors. depending on the voltage type (AC or DC) it could be as simple as resistance in the circuit. when you are talking about AC circuits, there are also capacitive reactance (Xc), inductive reactance Xl), resistance, variances in voltage (fluctuations) , frequency... also the "skin effect" must be taken into account. solid conductors(especially at higher frequencies), are susceptible to eddy currents within the conductor itself. meaning that current just circulates withing the center, forcing EMF (electromotive force) to the outer "skin" of the conductor.
What is Skin effect in transmission lines?
when a conductor is carrying a steady DC current,it is uniformly distributed over the whole cross section of the conductor. however, an alternating current flowing through the conductor does not distribute uniformly . Rather it has a tendency to concentrate near the surface of the conductor. This is known as skin effect
Why skin effect absent in dc system?
Skin effect is caused by the back emf produced by the self induced magnetic flux in a conductor. For a DC current, the rate of change of flus is zero, so there is no back emf due to changes in magnetic flux. Therefore, the current is uniformly distributed throughout the cross section of the conductor.
What is meant by skin effect?
The skin effect occurs in conductors carrying alternating currents, where the tendency is for the current to flow towards the surface of the conductor. The effect increases with frequency. At radio frequencies, the skin effect is so pronounced, that there is little point in using solid conductors, so tubes are used instead.The skin effect is responsible for the so-called 'AC resistance'. This is because the skin effect acts to reduce the effective cross-sectional area of a conductor, thus increasing its resistance compared to when a DC current passes through the conductor.
Does electric current flow only on the surface of the copper conductor?
The AC current tend to flow on the surface of the conductor. The higher the frequency, the thinner the skin. This is known as the skin effect. So DC current flow throught the entire conductor but when the signal varies (AC) there is the formation of eddy current in the conductor itself and that pushes the electrons at the surface of the conductor. You can get more information on the skin effect and skin depth on wikipedia : http://en.wikipedia.org/wiki/Skin_effect http://en.wikipedia.org/wiki/Skin_depth
Skin effect related to ac and DC?
IT IS RELATED TO AC ONLY BKZ SKIN EFFECT DEPENDS FREQUENCY ONLY WHERE IS IN DC NO FREQUENCY
What is difference between skin effect and franty effect?
skin effect that happen because the current pass at the edge of the cable in the ac current because of the frequency but in the dc the current pass throw the whole conductor the franty effect the stray capacitor increase the voltage on the line due to light load and the
What happens when a compass is palced near a current carrying conductor?
If the conductor is carrying AC, no effect. If the conductor is carrying DC, then the compass needle will be deflected. Provided the two are close enough, and the DC current is strong enough.
Which values of resistance is correct ac or dc?
AC current tends to flow towards the surface of a conductor due to what is known as the skin effect. This phenomenon acts to reduce the effective cross-sectional area of a conductor and, therefore, elevate its resistance. This elevated value of resistance is known as AC resistance.The skin effect increases with frequency. At 50/60 Hz, the skin effect is quite moderate and, so, the AC resistance is not significantly higher than the true (or DC) resistance of the conductor.As to 'which value of resistance is correct?' Well, the natural resistance of a conductor is directly-proportional to its cross-sectional area and resistivity, and inversely-proportional to its length and the type of current plays no part in this. This is the value that a DC current would 'see', so you could say that this would be the 'correct' value of resistance.
Why are AC and DC resistance different?
An AC current tends to flow towards the surface of a conductor due to a phenomenon called the 'skin effect', which acts to reduce the effective cross-sectional area of that conductor.Since resistance is directly-proportional to the cross-sectional area of a conductor, the conductor's resistance to an AC current is, therefore, higher than its resistance to a DC current (which distributes itself across the full cross-sectional area). We call this elevated value of resistance, AC resistance.The skin effect increases with frequency to such an extent that, at radio frequencies, there is little point in using solid conductors and tubes are used instead. At mains' frequencies (50/60 Hz), however, the skin effect is moderate and, so, the value of a conductor's AC resistance is only slightly elevated compared to its true resistance.It's important not to confuse the term 'AC resistance' with 'reactance', which is a function of a conductor's inductance and/or capacitance, and the frequency of the supply.
What is the difference between DC and AC resistance?
AC resistance should NOT be confused with IMPEDANCE or REACTANCE.When AC flows through a conductor, it tends to flow towards the surface of that conductor due to a phenomenon called the 'skin effect'. The skin effect, therefore, acts to reduce the effective cross-sectional area of the conductor. Since resistance is inversely-proportional to cross-sectional area, the result is an elevated value of resistance compared with that to DC current. This is called AC RESISTANCE, and it increases with frequency. At mains frequencies (50/60 Hz), AC resistance is not dramatically higher than DC resistance but the difference becomes significant at high frequencies.Read more in the Related link shown below this answer.
What is proximity effect in transmission line?
The current distribution in a conductor is affected by magnetic flux produced by current flowing in any adjacent conductors as well as by magnetic flux produced by current flowing in the conductor itself. This generally causes the RF to DC resistance ratio to be higher than it would be with only simple skin effect. This effect is very important in radio frequency coils, transmission lines, and most other circumstances where radio frequency currents flow simultaneously in adjacent conductors. It is known as the conductor proximity effect.
When an electric field is applied to a conductor does the electric field develops within the conductor or around the conductor?
The electric field will develop inside the conductor, depending on the characteristics of the electric field -- in a steady state (DC) or in an alternating mode (AC). The higher the frequency of oscillation, the shallower the field will reside in the conductor -- skin depth (check the related link). Hence, when the frequency is high, only the few mm's of the outer skin participates in the action (AC electrical conduction.) In steady state (DC), the frequency is zero, the electric field is distributed inside the whole conductor.
