Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [internal-resistance]

66 questions
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Why does my 120V 40W lightbulb only have 26 ohms across it?

I thought that if the voltage source is 120V and the lightbulb is 40W then the current would be 1/3 of an ampere meaning that the resistance of the lightbulb would be 360 ohms. But when I checked it with my multimeter, it was only 26 ohms. The…
ratsmisimo
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Does a battery's ability to supply high current mainly depend on its internal resistance?

I was posed the question of whether or not you would be able to start a car with 8 small 1.5V batteries in series (thereby creating the required 12V most cars run on). I immediately answered "no", with my reasoning being that the small AA batteries…
Gary Allen
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Under what conditions would using a voltmeter be more accurate than an ammeter to measure current?

Suppose you have a simple circuit with a voltage source V1 connected to a resistor R1, like this: simulate this circuit – Schematic created using CircuitLab You could connect an ammeter in series, and then the internal resistance of the ammeter…
kieransquared
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How do multimeters work?

I am helping a high school student with a physics experiment on internal resistance of a cell. My background is in chemistry, not physics. Browsing SE for lab design, Measurement of internal resistance of a battery pops up. Now the high school lab…
okzoomer
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Contradiction:Maximum Power Transfer and High resistance of load

Whenever we load a circuit, there's a drop from the open circuit voltage \$v_{oc}\$ due to the internal source resistance or Thevenin's resistance\$R_{th}\$. So we need to have an \$R_{load}\$ that is very large compared to \$R_{th}\$, (i.e)…
Aravindh Vasu
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At what charge of a battery should its internal resistance be calculated?

I am trying to determine a battery's internal resistance using the open circuit voltage, terminal voltage, and load current for each battery cycle. As per my current understanding, these calculations must be conducted at a particular charge of the…
Noor
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Decrease of internal resistance of a solar cell while increasing the load resistor?

Imagine to model a solar cell as a power supply \$V_p\$ in series with an internal resistance \$R_p\$. This solar cell is connected to a variable load resistance \$R_{load}\$. Suppose that I keep the solar cell at fixed distance from a fixed light…
Sørën
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Is a battery's internal resistance a function of integrated current over time?

I've got a question regarding the internal resistance of a CR2032 coin cell. Here's some background info on the project I'm working on: I'm working on an electronics project in which I hope to have battery powered, more specifically I would like it…
Izzo
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Measure a lithium-ion battery internal resistance curve over time

I am making a battery tester for lithium ion batteries. I want to measure the internal resistance, voltage and current. I am skeptical of my results. On batteryuniversity, I read that the internal resistance curve should start and end with higher…
Khalil
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Is the process of adding new parallel (matching) cells into an already built battery pack safe?

I just built a 5p13s 18650 li-on battery pack with a bms. I realized after the build I add more of the same cells (all new), so I could have built a 7p13s instead. Is it possible, after setting the new cells to the same voltage as the ones in the…
mikmikmik
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Question about battery internal resistance measurement

I have a 65 mAh thin Li-Po pouch cell. I tried measuring the internal resistance of the same using the foll. steps: (The battery was fully charged before this process) Battery open circuit voltage measurement: 4.0662 V Connect a 560 ohm resistor…
Ved Soni
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18650 pack building - is it better to have similar batch or similar capacity?

I'm gonna build battery packs. I have quite a lot of experience with 18650 Li-ion cells, but there's one thing I still don't know. I will buy CCA 100 new cells from seller (for example LGEBHE21865). There are multiple batches of cells (the number…
x-fox
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Difference between analog signal and battery voltage

I want to find out if using an analogue sensor is feasible in my noisy environment by running some signal integrity tests before I buy it. Because I don`t have the sensor yet, I need to simulate its output. This can be assumed to be a constant DC…
user211492
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What extra battery information do you get by using a two tier dc load method VS the one tier method?

I learned that these of these two methods the one-tier method can only measure the internal resistance of a battery but you get more information from the two-tier testing method. However, the resource I was reading either didn't specify the benefits…
Matthew3302
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How to derive equation for current from parallel batteries given internal resistance and load?

I'm studying DC circuits in physics right now and have come across this frustratingly unclear part of the textbook. Apparently, the current through a circuit given ideal emf, internal resistance, and circuit load is \$I = \frac{\epsilon}{r_{eq} +…
TheRealNoofle
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