A resistor obeys Ohm's law (V=IR); the current through it is equal to the voltage across it divided by the resistance (equivalently \$I=\frac{V}{R}\$)

learn more… | top users | synonyms (1)

0
votes
1answer
38 views

Max handling power for a 10w speaker resistor

I have been told that a speaker resistor can only handle 10 watts if it is a 10 watt resistor, which makes no sence because they do use even 5 watt resistor in a 160 watt setup. So my question is how ...
0
votes
1answer
52 views

Can you explain how the following garden solar light circuit works?

I found the following circuit in a solar garden light. The cut off white and black wires are from the solar panel. What does the 4 pin transistor do?
0
votes
1answer
40 views

ambiguous component values (ex. U01 U47 M47 etc.)

i'm having a hard time understanding components value when it's given in the following formate U01 U47 M47 sometimes it's even worse like 4N7 i know that U for micro, M for mega, N for nano but i ...
0
votes
2answers
55 views

Unexpected results when trying to amplify voltage across a wheatstone bridge

I am working on a project, and am trying to amplify the voltage across wheatstone bridge. Here is the diagram: where \$R_1 = 1,000 \Omega\$ \$R_3 = 10,000 \Omega\$ and \$R_2\$ is a ...
0
votes
1answer
84 views

Solving a source free series RLC circuit

How do I proceed to solve this problem. If I write a KVL equation, I get $$4 (4 Vc) +1/10^-3 integral i dt - 10=0$$ What to do next?
2
votes
2answers
56 views

Closed circuit vs low resistance resistor

I'm learning electronics and this confused me. In this circuit it shows that current flows through both wires with resistors and lower only through one wire where there's no resistor (even though one ...
1
vote
2answers
84 views

How does Current relate to Voltage in their behavior in our physical world [duplicate]

I'm really an electrical noob who tries to understand voltage, current and resistance. I know the formulas and can somehow come up with basic explanations about the physics of electricity. However, ...
0
votes
0answers
29 views

Finding the current through resistor in source free parallel RLC Circuit for t>0

My solution: Since alpha >w0, so response is overdamped. Current through inductor:$$ Il(0-)=Il(0+)=6 $$Voltage across capacitor: $$Vc(0-)=Vc(0+)=0V$$ Current through resistor: $$ Ir(t)=A1e^{s1t} + ...
0
votes
2answers
68 views

A question about E12 series resistors

I'm trying to calculate E12 resistor series myself. Above is an illustration of the idea where such equation can be written: x = r3 + r3 * %tol = r4 - r4 * %tol form that we can derive: r4 = r3* ...
0
votes
1answer
52 views

Vendor charging radically different prices for different value resistors, why? [closed]

Over the years I have optimized my parts sourcing. I am now dealing with a new vendor whose prices are much better than previously, but they have an annoying quirk -- they charge different prices for ...
1
vote
3answers
103 views

Is this a power resistor?

I'm trying to repair an electrophysiology amplifier (AXOPATCH 200A). It has this power resistor which I desoldered because I suspected it was broken. The color code (red, green, black, gold) gives 25 ...
0
votes
2answers
44 views

How were values of Vc(0+) and i(1.5ms) found?

I get that by applying source transformation, we get a (0.1*200=20 V) source but shouldn't 0.1 A current be divided into 50 ohm and 100 ohm resistance? Also why i=0 at t=1.5ms?
0
votes
1answer
70 views

Resistance of twin core wire

I'm trying to do a problem for revision and I'm running into problems calculating the resistance of this circuit used to approximate a twin-core wire. It's used later in the question with the middle ...
0
votes
3answers
103 views

How was this equation for finding current written?

It doesn't make any sense because at \$t\gt 0\$ the two circuits are disconnected (the left and right portion). How has \$25 i_x\over 20\$ been calculated?
1
vote
1answer
38 views

Ethernet driver Circuit

I've been working on Ethernet schematics, i noticed a network of capacitor and resistors present outside the RJ45 connector. For what reasons these passive components are used? I've attached the ...
0
votes
1answer
55 views

why add a resistor parallel to voltage source? [duplicate]

Sometimes I see a resistor parallel to voltage source (such as image below), isn't it completely useless ? Edit: I see the other similar question now, but I think it doesn't have the right keyword ...
0
votes
1answer
89 views

short circuit - Time constant calculation

In calculating Tao,why can't you ignore the shorted resistors? capacitor goes to natural response when the gate shuts. \$\ v (t) = Ve^{t/T}\$ here T, is \$\ T= R_{eq}C \$ Since there is no ...
0
votes
0answers
22 views

RC Relaxation Oscillator Problems

I found a schematic for this oscillator online here and I tried it, but instead of the LED turning on and off sawtooth style, it got brighter slowly, and stayed bright without getting dimmer. What is ...
1
vote
2answers
51 views

Rule of Thumb When a Bleeder Resistor is Advisable

New to building circuits, I’m trying to develop an understanding as to when a bleeder resistor should be connected across a capacitor for safety reasons. I’ve seen several references talking about how ...
1
vote
3answers
81 views

It is possible to exist more than 1 color code for same resistance. Can i use all of these color-codes?

It is possible to exist more than 1 color code for same resistance-value. I doubt, is there any convention about use only one of them (while manufacture) . Example : Say an 1 ohm resistor could be ...
5
votes
2answers
400 views

What's a potentiometer with four terminals in this schematic?

I'm reading the datasheet for a TDA2005 IC. In it, there's a application circuit schematic with two potentiometers that have a fourth terminal in it. See below: The components I'm talking about is ...
1
vote
3answers
53 views

Adjustable Voltage Regulator Resistor Values

I'm working with an adjustable voltage regulator and am having a hard time understanding my equation for determining resistor values. Datasheet: ...
0
votes
3answers
78 views

Switch mode PSU minimum load

Alright, I know I am going to get a lot of flak for this, but let me reassure you that I have already spent the last few days reading on Google while going back and forth from the bench to test ...
1
vote
1answer
82 views

what is the use of a resistor in the PNP transistor?

The R3 is connected to the output of the PIC, I could understand the NPN transistor but PNP was a bit confusing. When the transistor starts to conduct, some current will flow towards the base. My ...
3
votes
4answers
248 views

The potentiometer used in electronics is not a measuring instrument. Why it is called a meter?

Why this kind of variable resistor is called a "meter", when it is not a measuring instrument? I have seen another instrument of same name. In our school physics lab, there was a big rectangular, ...
1
vote
5answers
117 views

Difference between current and power

I am a bit confused about the difference between current and power. I am hoping someone can explain the difference to me maybe using an analogy or something. I do understand that current at a point ...
0
votes
2answers
71 views

How to calculate the base-current of this transistor?

Newbie in eelctronics here. How would you calculate the current trought the base of the first transistor? simulate this circuit – Schematic created using CircuitLab follow-up question: ...
0
votes
1answer
42 views

RC filter with an square wave input (checking my math and find my error, if it is somewhere) [duplicate]

I've this RC filter circuit (r is connect to earth on the bottom): My Vin is a square wave: With Laplace transform I derived that: $$Vout(s)=\frac{r}{r+\frac{1}{cs}}\cdot Vin(s)$$ and this ...
0
votes
1answer
58 views

RC filter with an square wave input

I've this RC filter circuit (r is connect to earth on the bottom): My Vin is a square wave: With Laplace transform I derived that: $$Vout(s)=\frac{r}{r+\frac{1}{cs}}\cdot Vin(s)$$ and this ...
-3
votes
2answers
97 views

How do I know if I need a resistor or not? [closed]

I have bought a Sound Bomb from Maplin. On the bottom of the device it says: Voltage (DC): 12v Voltage Range: 6-15v Current: 85mA If I want to wire this ...
0
votes
0answers
23 views

How is the standard values of resistors and capacitor defined/decided? [duplicate]

How is the standard values of resistors and capacitor defined/decided? How come some values exist but not others?
0
votes
1answer
48 views

Current Limiting Resistors for Multi-Branch LED circuit

I have bought some of the following LEDs (going to try either for brightness/size): 100 Pcs 0603 SMD Superbright LED Yellow Light Emitting Diodes 40 Pcs SMD 1206 LED Lamp Yellow Light Emitting ...
0
votes
2answers
115 views

How to combine LED and voltage divider

I want to detect the presence of a 8.4V voltage source from an Arduino, so I'm using a voltage divider to step it down to a voltage safe for the Arduino to read with an digital pin. However, for when ...
-2
votes
2answers
156 views

Why do we use resistor along with the transistor?

from the knowledge i have, i know that a transistor is a special kind of resistor that can change it's resistance depending on the input at it's base. questions sorry for the big picture => Why do ...
1
vote
0answers
47 views

an LM13700 can be configured as a “floating” voltage controlled resistor ; How resistor-like is it?

I want to use an LM13700 as a voltage controlled resistor, and I want it to act like a rheostat. When will it act non-linearly? The description of this circuit is on page 15 of the datasheet, and ...
1
vote
1answer
36 views

Thin film SMD resistor reliability

I am hoping someone can point me toward some clarity regarding the durability of thin film SMD resistors. Google pointed me toward a number of pages that indicate they are sensitive to humidity and ...
0
votes
0answers
30 views

Estimate kanthal's temperature by power dissipation

I've a bare Kanthal A-1 wire, And I want to Estimate it's temperature, basically to make a °C vs W plot. In this post Thermal resistance is used to do it as: ...
0
votes
2answers
104 views

Which Multimeter is correct?

I have two Multimeteres that I'm using to measure resistance of a 10 Ohm resistor. Now, when i measure with the first one it's showing 10.2 Ohms while the other is constantly changing values from 9.9 ...
0
votes
1answer
61 views

(Design) Resistor on anode or cathode? [duplicate]

I was recently confused on where the resistor would go on the circuit. I then learned that it didn't matter. Is there a standardized sequence for the placement of resistors? For example, battery -> ...
0
votes
0answers
35 views

AC equivalent circuit -BJT

For the following circuit, I'm asked to give the AC equivalent circuit for small alternative signals. On the second circuit (the one they gave us as a solution), I don't understand why they didn't ...
1
vote
1answer
42 views

ferronickel temperature coefficient

I'm heating a ferronickel wire, and I need a reliable measurement of temperature, I was using a thermocouple to do this measurement but the wire is cooled when it's touched by the thermocouple so now ...
0
votes
0answers
37 views

ESP8266 using LOW-Level with GPIO0

as you know to put ESP8266 into bootmode GPIO0 should be connected to the ground. That works perfectly, but the problem I don't ...
0
votes
1answer
88 views

What is the purpose of resistance & capacitance in parallel to Load ( refer ckt )

What is the purpose of resistance & capacitance in parallel to Load ( refer ckt ) ? As per my understanding these capacitor & resistor is for filtration purpose ( kindly clarify the same) . ...
-6
votes
2answers
123 views

Can i put a resistor in backwards? [duplicate]

Simple, curious, yes/no question: Can you put a resistor in backwards?
0
votes
0answers
71 views

Can some help me understand this ground switching circuit?

I am trying to understand a switch circuit related to a project that I am working on. Pin 1 - 12v signal for switch backlights Pin 2 - 12v signal for switch on/off indicators Pin 3/4 - Unused Pin ...
0
votes
1answer
78 views

Problem with high-pass filter - signal gets shifted down

I have a problem where I am passing pulses received from a photo-diode into a high pass RC filter. Circuit shown below. The pulses are being received at 25Khz. Before the filter, the pulses are ...
4
votes
5answers
128 views

Rules for choosing power rating of a resistor

Let's say we're designing a system, and within it we have some resistor \$R\$ with a voltage difference \$V\$ across its terminals. Then it dissipates power \$P = V^2 / R \$. Of course the resistor ...
1
vote
1answer
29 views

Need help understanding the concept of “Circuit model of a discharging RL circuit”

I don't understand the statements for t<0 and t>0. Why does this happen?
0
votes
0answers
37 views

Series Gate Resistor needed at low Capacitance?

even though this question has been answered before for various scenarios, I would like to ask for a generic advice. So I want to drive a certain resistive load from a microcontroller pin. Let MCU be ...
0
votes
1answer
67 views

What resisters for inverting op-amp should I use?

I am not an electrical engineer by any means so go easy on me here. I am simply experimenting with a speaker amplifier. My situation: I have a Clarion xc1410 4-channel amplifier with a 10k input ...