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Fixed-value resistors are normally manufactured so that they obey Ohm's Law -that is, the ratio of their voltage to current remains constant for variations in voltage, within specified limits. In other words, their resistance value remains constant for variations in voltage. This would produce a straight-line curve when plotted. Devices and materials that do not obey Ohm's Law (e.g. semiconductors, etc.) would produce a curved line.

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Q: What is the nature of the current voltage graph for an unknown resistor?

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A resistor doesn't have a power factor. However, if a circuit is pure resistance in nature the power factor will be one when a voltage is applied and a current flows in the circuit. The power factor is a measure of the relative phases of the current and voltage in a circuit.

Leading and lagging currents are not so much "currents" as they are "situations" or "conditions" in an electrical circuit. Reactive characteristics, if there are any, will not let voltage and current be in phase in a circuit. (Unless they are equal, and this will be true at only one frequency.) In some circuits, current leads voltage (or voltage lags current), and in other circuits, current lags voltage (voltage leads current), depending on the circuit and also on the frequency of the applied signal. In a capacitor, current leads voltage, and in an inductor, current lags voltage. This carries over to circuits that exhibit primarily capacitive or inductive characteristics. Additionally, reactance varies with frequency. As a given circuit with inductance and capacitance is evaluated, at some frequencies, it will appear capacitive, and current will lead voltage. At other frequencies, the circuit will appear inductive, and current will lag voltage. Only at a frequency where the reactances are equal will the current and voltage be in phase. The ideas here are best reviewed after achieving an understanding of the nature of inductance and capacitance, the associated reactances, and the way frequency affects these characteristics.

AC voltage is varying because it is sinusoidal in nature

DC is direct current. It is characterized as a voltage or current that is constant or, more precisely, always in one direction. A battery is an example of a DC source. AC is alternating current. It is characterized as a voltage or current that is alternating, i.e. changing direction at some frequency such as 50Hz or 60Hz. The power supplied to your home from the public power utility is an example of an AC source. ac is attractive in nature while dc is repulsive .

DC voltage refers to "direct current," and it can mostly be found in batteries. It means that it flows constantly through the circuit, as opposed to AC (alternating current) which switches flow quickly. There are benefits and downsides to direct current, the benefits being that it is best suited for low-current applications and is easy to work with, the downside being that it loses energy quickly as it flows and cannot reach very high power (voltage).AnswerIn this context, 'd.c.' is being used as an adjective to describe the nature of the voltage.

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A resistor doesn't have a power factor. However, if a circuit is pure resistance in nature the power factor will be one when a voltage is applied and a current flows in the circuit. The power factor is a measure of the relative phases of the current and voltage in a circuit.

Your question reveals fundamental misunderstandings about the nature of electricity.'Voltage' is simply another word for 'potential difference', and a potential difference appears across opposite ends of the resistor; it doesn't 'travel through' that resistor! Current, on the other hand, DOES 'travel through' the resistor and is caused by the potential difference across the resistor.Resistance is the ratio of potential difference to current. So if the resistance remians unchanged when the current through it doubles, then it has happened because the potential difference has doubled.

vsi's output voltage is independent of load nature, but output current is depends on load nature. csi's output current is independent of load nature, but output voltage is depends on load nature.

resistive in nature like an incandescant lamp

That's an "open circuit". No current flows no matter how high the voltage gets. It doesn't exist in nature.

Ohmic (or 'linear') materials obey Ohm's Law. That is, their ratio of voltage to current remains constant for variations in voltage. Ohmic materials, therefore, produce a straight line graph when we plot current against variations in voltage;Non-ohmic (or 'non-linear') materials do not obey Ohm's Law. That is, their ratio of voltage to current variesfor variations in voltage. This means that non-ohmic materials produce a curved line graph when we plot current against variations in voltage.

Yes, increasing the voltage to an electric heater will typically result in an increase in the amperage it draws. This is due to Ohm's Law, which states that current (amperage) is directly proportional to voltage and inversely proportional to resistance. As voltage increases, the current drawn by the heater will also increase.

Leading and lagging currents are not so much "currents" as they are "situations" or "conditions" in an electrical circuit. Reactive characteristics, if there are any, will not let voltage and current be in phase in a circuit. (Unless they are equal, and this will be true at only one frequency.) In some circuits, current leads voltage (or voltage lags current), and in other circuits, current lags voltage (voltage leads current), depending on the circuit and also on the frequency of the applied signal. In a capacitor, current leads voltage, and in an inductor, current lags voltage. This carries over to circuits that exhibit primarily capacitive or inductive characteristics. Additionally, reactance varies with frequency. As a given circuit with inductance and capacitance is evaluated, at some frequencies, it will appear capacitive, and current will lead voltage. At other frequencies, the circuit will appear inductive, and current will lag voltage. Only at a frequency where the reactances are equal will the current and voltage be in phase. The ideas here are best reviewed after achieving an understanding of the nature of inductance and capacitance, the associated reactances, and the way frequency affects these characteristics.

Yes, both Kirchhoff's Current Law (KCL) and Kirchhoff's Voltage Law (KVL) can be applied to both AC (alternating current) and DC (direct current) circuits. KCL states that the sum of currents entering a node must equal the sum of currents leaving the node, regardless of the type of current. Similarly, KVL states that the sum of voltage drops in a closed loop circuit must equal the sum of voltage rises, a principle that applies to both AC and DC circuits.

In circuit equivalence, voltage and current sources are respectively equated to short and open ckt because of the very nature of them. A voltage source has zero internal resistance and current source has infinite internal resistance hence their equivalents:-)

AC voltage is varying because it is sinusoidal in nature

The nature of your question suggests that you are trying to convert 18VDC down to 3.3VDC Perhaps to power a microprocessor running at that voltage. If you just used a simple divider circuit then there would be two resistors involved, not just one. You cannot "take" 18VDC down to 3.3VDC with a single resistor. You could limit current but not "divide" the voltage down. Really a divider circuit is not the best way to do this either because you probably want to draw at least some current at the 3.3V level. A simple divider circuit voltage would be dependent on the load.. So... I would recommend either a switching or a linear regulator (non switching, and not very efficient). There are a bunch of DC-DC switching regulators that would do the job nicely... I like the ST Micro L5981. It will output up to about an amp at 3.3V and work from 2.9V to 18VDC input. You can find the datasheet athttp://www.st.com/stonline/products/literature/ds/13004.pdfOh, and I'm not pushing the STMicro solution, there are many other good regulators available from Analog Devices, Linear Tech, as well as TI, and National... So Google a bit and you will discover many things for yourself...