# Questions tagged [resistivity]

A direct measure of how resistive a material is with higher numerical values meaning that the material is more resistive. It is the inverse of conductivity. The units of resistivity are $\Omega* m$ or $\Omega* cm$ (in the semiconductor industry) - not to be confused with resistance that is similar but does not have units of length associated with it.

29 questions
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### High temperature electrical heater

I've been trying to put together a relatively simple electrical circuit to heat an electrode to 750 degrees celsius. In theory, is it simplest to persist with using several car batteries (not those to ...
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### voltage amperage ratio for resistive heating of glass [closed]

I am planning to introduce electric heating/boosting in my glass melting furnace. The present temperature of the glass is around 1200 deg C and I need to raise it up to 1300 deg C. I am trying to get ...
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### How does capacitive sensing relate to the resistance of the object entering the magnetic field? [closed]

Example: Setting up a capacitive area and dropping resistors of different sizes into the field, how do they affect the field differently? Are several resistors accumulative? Would i be able to tell ...
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### Exactly what type of resistor is being referred to in this diagram?

I'm trying to control an RGB LED strip using a NodeMCU. I have been following the guide linked here. However, the diagram included in the diagram is rather unclear, especially for someone like myself ...
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### Thermal resistance of a wire of copper

I was reading a book about thermal heat conduction and resistance, when I found the next example: Try to calculate the temperature of a 4-in(0.1m) piece of #12 copper wire at the end that is being ...
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### Resistivity of Ferromagnetic Substance

How does the resistivity of a ferromagnetic material change as the material is being magnetized (magnetic domains aligned)?
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### How to calculate size of metal plate for a specified current?

So I'm looking at running a plate from the terminal of a battery (26650) and I'm trying to calculate the width of the plate needed given a certain thickness and length as well as a specified current. ...
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### Nichrome wire gauge calculation

I know what battery I wish to use (3.7 V 140 mAh which I can swap for larger mAh battery) I know what length of wire (3.5 inches or 7 inches depending on which ever would work better) I know what ...
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### How do you determine the effective resistance of a finite grid of resistors?

Disclaimer: I am a geophysicist with limited electrical engineering background. I am not sure if this problem is incredibly easy, incredibly complex, or completely nonsensical. My goal: Determine the ...
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### Are values of resistivity independent of the cross-section and length of the resistor?

I was reading resistivity values for different materials on the wikipedia page. They report the values for standard temperature, but they give no information about the cross-section or length of the ...
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### I am trying to make a electro magnet. I bought a coil of enamel copper wire from Ebay. How do I determine its resistance?

I didn't even know you need AWG rating to get a coil's resistance. But this is may sound naive, can I use the physics formula: $$R=\rho\frac{L}{A}$$. $\rho$ is resistivity of copper, which I looked ...
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### Electrical resistance of two conductors of equal surface area in contact with another?

Resistance of a wire can be determined by the formula R = resistivity*(length/area). What if you have a wire composed of two parallel metals that are in contact with one another? Will the resistivity ...
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### Voltage drop remaining voltage [duplicate]

According to here the resistance drops liniar along the path. In scenario 1 at the start of R1 the resistance the current encounters is 100$\Omega$ and at the ...
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### Computing the electric potential generated by a current density across media with different conductivities

Model: a right cylinder composed three layers of conductive media. The is a disk of unit charge density in the center of the cylinder. The disk radius is equal to the cylinder radius. The outer layers ...
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### MOSFET resistor, difference with no gate or gate at 0V

While measuring a MOSFET resistivity without a gate voltage I have observed that the resistivity obtained for a gate voltage at 0V is 20 times higher than the resistivity observed when there is no ...
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### Incandescent bulb for 220V vs 110V and difference of their resistance?

I know that 40Watt,110V incandescent bulb has about 302 ohm resistance of tungsten filament (which is metal and of course have low resistivity) comparing it to 40Watt, 220V bulb which has about 1200 ...
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### Resistance and Resistivity [closed]

How do I calculate the radius of a copper wire dissipating heat of 100mW given that the volume of the conductor is 20mm^3 and is carrying a current of 40nA. Resistivity of copper is 0.0000172.
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### What is the identity of this shiny insulator?

fig: Shiny layer I've seen many times, on metallic objects, a kind of insulator layer is given (I've tested its resistance with multimeter and it shows infinite ohms). The layer is greenish-gold in ...
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### Is there an internal resistivity in buzzers?

I would like to know if there is an internal resistance in buzzers, and if yes, what could be the internal resistance for a cheap buzzer that can go up to 12V. Thank you
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### High Temperature Conductor in Air

I am trying to determine what the best material is for a high temperature conductor. It is for distributing power inside a furnace. I need to run at around 1000 celsius (the furnace is hotter but this ...
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### voltage drop & resistivity calculation

I wanted to implement below formula into excel sheet. can someone suggest me with example. cable equation example : system voltage =12v, sys current=8A, length in feet=50. Resistance = resistivity* ...
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### nichrome alternatives

I am repairing an AVO multiminor Mk 4 which was in a sort circuit across a car battery while in the 1 amp measuring position. circuit diagram here an obvious casualty was the 0.25 ohm resistance R1 ...
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### Given metal dimensions and material, is it possible to determine the maximum current that the structure can handle? [semiconductor processing]

I have a linewidth structure that has very low resistance. I want to know the maximum current that this structure can handle. Since the resistance of the metal is so low, it's hard to measure the ...
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### Minimum electrical resistivity of contact material for human protection from lightning

The context of the question is camping and sleeping outdoors in the unprotected elements. If you’re sleeping in a tent close to the ground, and lightning directly strikes your tent or the vicinity ...
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### Why are the Resistance/Resistivity Equations Formulated as they are?

The equation for temperature dependence on resistivity: $$\rho(dT) = \rho(0)(1+\alpha dT)$$ where $dT$ is change in temperature from some reference and $rho$ is resistivity. This leads to ...
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### Can the resistance between two points in air be calculated? How?

If I have just a battery, the terminals are separated by air, a very good insulator. We can say, practically, that no current flows. However, air has a very large, but finite resistivity. Wikipedia ...
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### Wire resistivity

Could you please shed some light on wire resistivity calculations for me.... for example if you have a wire length at 100m with a diameter of 10mm measured at 0.25 ohms.(what material is 0.25?? I can ...