# Questions tagged [internal-resistance]

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73 views

### Why do heating elements burn out? [closed]

I want to build a heat transfer machine, and want to build it from an electric pressing iron heating element, but then someone told me the heating element can burn out. How true is this? Thanks
44 views

### 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 ...
77 views

### Series internal resistance of Power Supply

I have this power supply - GPC-3030D There are 3 independent channels. 2x (30V/3A) and 1x (5V/3A) To find the internal resistance of the voltage source channels, its just 30V/3A = 10Ohms and 5V/3A = ...
68 views

### Measuring battery resistance

I am trying to measure the resistance of a AA alkaline battery. The circuit I am using is shown in a photo below. I have also attached the values I obtained. Somehow, the values I am getting ...
66 views

### 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 ...
40 views

### Max power transfer of source with variable internal resistance

I have been reading how to obtain maximum external power from a source using the maximum power transfer theorem. However, it is for a source with a finite internal resistance. Can you have power ...
368 views

### Transistor internal resistance

Does a transistor have an internal resistance, because when I run a circuit simulation in proteus I discovered that bc547 has a collector to emitter resistance of 99ohms... Does that apply to real ...
51 views

### Battery output power calculated from internal resistance - explanation, relation to heat generation and actual power?

On a battery manufacturer specification (https://www.scib.jp/en/product/cell.htm, "High power 10Ah cell") it says: Output power 1800W* (SOC:50%, 10s, 25°C), *This value is calculated from the internal ...
82 views

### Voltage dip at source side during heavy loads due to Internal Resistance

In any application, during initial start-up/load step, there is an high current requirement. Due to this high current requirement, there is a dip in that connected voltage rail. I researched on why ...
40 views

### Should we include Source and Load Impedance while calculating two port parameters?

While calculating the $Z$, or $Y$ or $h$ parameters of a two port network, should we include the source impedance and load impedance or not? In other words, for finding $Y_{11}$, we short the ...
95 views

### 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). ...
53 views

### What is the internal resistance of a LiPo battery determined by?

Given DKNguyen's answer to my last question, I wanted to know what determines the internal resistance of a LiPo battery. Does it have something to do with its inside chemistry? Is it just roughly ...
658 views

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 ...
68 views

### Should series connected battery cells have similar internal resistance and to what degree?

I have some Toshiba SCiB cells that I wish to string in 4s configuration. These are Lithium Titanate (LTO) cells. They have a 20Ah capacity and operate safely between 1.5 V and 2.7 V. The cells were ...
514 views

### 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 ...
48 views

### Battery Bank total internal resistance

Let's assume you have a battery bank not connected to anything and we are dealing with perfect ideal values. You just want to calculate the total battery internal resistance of your battery bank. To ...
422 views

### Do rail gun systems require high voltage?

I couldn't justify, as to why most rail-gun examples I found would have high current and high voltage. When the rails & projectile can be designed to have low resistance by varying the volume of ...
202 views

### Internal resistance of LDo

I was trying to measure the internal resistance of an LDO that will produce 2.85V. I used a Digital multimeter to do this, but I got a resistance of 810 Ohm and the LDO can support upto 450 mA. Will ...
563 views

### Under what circumstances would the large internal input resistance of an actual op amp affect circuit operation?

I was able to find a lot about why the input resistance is high and basically infinite. I understand that the input resistance is high so that it doesn't become a load on the signal. I also know that ...
3k views

### Finding the Internal Resistance of an Ammeter using a shunt

There is this lab procedure to determine the internal resistance of an ammeter which differs from the usual process. In this new procedure, we connect a voltage supply in series with a resistor of ...
813 views

### Internal Resistances of Capacitors

I have read somewhere on a forum that there are two effective internal resistances of a capacitor in a DC circuit but can't seem to find any further information. From what I read 'parallel resistance' ...
460 views

### Can you calculate internal resistance of battery by shorting it?

Can I measure the current of a battery by shorting the circuit and by ohms-law divide the voltage of the battery by the current measured to get internal resistance?
551 views

### Measuring the Internal Resistance of an Electrolytic Capacitor

I was wondering if its possible to measure internal resistance of a capacitor from a DC circuit using the below formula and method. $\ V=V_0e^{\frac{-t}{\tau}}$ $\ lnV=-1/\tau\ *t + ln V_0$ ...
342 views

### Electrolytic Capacitor Internal Resistance

I'm doing an experiment to investigate the internal resistance of an electrolytic capacitor in a DC circuit. Doing this I am measuring the discharge voltage against time, finding tau and from there ...
435 views

### What is the recommended battery chemistry for digital multimeters?

I would like to know if the different internal resistances of different battery chemistry somehow affects the calibration of a digital multi-meter. If so, then what would the optimal battery ...
138 views

### Input resistance of a BJT common-emitter amplifer

What's the input resistance of the circuit below? I think it is $R_{in}=R_B || r_\pi$, but I am not sure
1k views

### Internal Resistance of a Supercapacitor

I am attempting to replace a wall plug power supply with a supercapacitor. From analysing the behaviour of the wall plug I can see that the current drawn is .25A with 800ms spikes of 1.5A (as ...
1k views

### 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 ...
1k views

### How do I measure internal resistence of voltmeter without ammeter?

I know how to do it with ammeter, but how can I find internal resistence without ammeter?
3k views

### Maximum current is drawn from a cell when it is shorted. But, why?

First, I must apologize for the trivial-sounding question. We've only recently started with Current Electricity in class, and our teacher posed this question (well, something similar) to us. For ...
540 views

### What might cause a fluctuating resistance of a generator winding?

Before assembly of a machine that contains a three phase generator I check the resistance between the 3 phases of the generator with an ohmmeter. The generator is kept stationary and the temperature ...
2k views

### JFET - transconductance, gain(mu) and internal resistance at the drain

Hello guys, here is such assignment: to determine gm, internal resistance at the drain and maximum gain (mu). 1) If Transconductance gm can be found from the formulas and graph. 2) How to determine ...
3k views

### Real output resistance of MOSFET

This question is related to MOSFET. NMOSFET's resistance was till now defined in many different ways, for example as: or which value varies from 1-50k Ohm. And there is also drain-source on-state ...
84 views

### Is the series resistance of an analog ammeter the parallel equivalent of shunt resistor and resistance of galvanometer?

An analog ammeter is made by a galvanometer (with certain $i_{max}$ and resistance $r$), in parallel with a shunt resistor $R_s$ that depends upon the max scale chosen. Nevertheless, when an ...
78 views

### Constant voltage term in model of diode with internal resistance

Ideal diode equation is $$V(I)=\eta V_T \mathrm{log}(\frac{I}{I_s}+1)$$ Model: simulate this circuit – Schematic created using CircuitLab If the diode has an internal resistance $r$, a more ...
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### “Equivalent resistance” of diode as $V/I$ used to evaluate an approximation

Consider the circuit in picture, used to measure the voltage across diode and current flowing through it. simulate this circuit – Schematic created using CircuitLab With this circuit I do ...
2k views

### 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 ...
8k views

### Hexagonal resistor circuit (equivalent resistance ) [closed]

I've already find the equivalent resistance between A en B by Star-Triangle transformation , but can someone just explain how can i handle it by Symmetry,asymmetry network analysis ? all the resistor ...
454 views

### Impedance of BNC vs output impedance of function generator

I'm a bit confused on output impedance of function generator and coaxial cable impedance. Consider a function generator with output impedance of $50 \Omega$. Suppose that I connect to it a BNC \\$...
3k views

### How to calculate internal generator resistance?

What's the formula for calculating generators internal resistance in a circuit with a load? I am given the load resistance and the voltage sources voltage. What's next? simulate this circuit – ...
3k views

### Multimeter current measurement: internal resistance or input impedance specification

As the internal resistance (or input impedance) of a multimeter influences the circuit you are measuring, and therefore influences the reliability of you measurement, it would make sense to me to if ...
549 views

### Relation between internal resistance and chosen scale on analog/digital voltmeter/ammeter

On Introductory Circuit Analysis of Boylestad I found out the following about the relation of internal resistance of a multimeter with the scale choosen on the instrument. Analog voltmeter: internal ...