56
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Accepted
Am I insane to question that only with a closed path can electrons move?
You are completely right.
The "closed loop" rule comes from a simplification that we often use in circuit analysis called the "lumped component model". This model provides a good approximation to ...
- 178k
28
votes
Can a thyristor be built from two transistors?
There are two easy kinds of thyristors made out of two BJTs. One is the SCR and the other is a PUJT. (The PUJT will use the base of \$Q_2\$ instead of the base of \$Q_1\$ as the gate -- see circuits ...
- 78.7k
23
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Am I insane to question that only with a closed path can electrons move?
Responding to your title:
Am I insane to question that only with a closed path can electrons move?
Currents usually* travel in loops. However, the loops need not be entirely made of conductors (ie,...
- 81.6k
23
votes
Accepted
Do higher voltages cause heating?
Yikes! You should count yourself lucky that nothing caught on fire when you did that, and you should never again plug a device into 240 V if it isn't rated for 240 V.
Your hair dryer is more or less a ...
- 3,489
21
votes
Can a thyristor be built from two transistors?
Yes, it's easy. You would typically want to add base-emitter resistors to one or both transistors to control the trigger and holding current.
Here's a simulated SCR that triggers at about 400uA gate ...
17
votes
Am I insane to question that only with a closed path can electrons move?
Rule #1. There is no such thing as an open circuit except under DC steady state conditions.
Between every wire, every part and even every atom, there is capacitance, resistance and inductance to some ...
- 47k
17
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Accepted
How do I really calculate these resistors?
You've done the calculations correctly, but the entire basis for the calculations is just a rough approximation of transistor behavior. As you see, \$V_{BE}\$ isn't really exactly 0.7V (most of the ...
- 31.7k
15
votes
Accepted
Meaning of Sigma in Laplace transform
As most folk know, \$s=\sigma+j\omega\$ (where \$j\omega\$ is the frequency along the x-axis in a bode plot or spectrum analysis). However, in a bode plot, \$\sigma\$ has no apparent meaning but it is ...
- 473k
15
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Accepted
Does a resistor between two pairs of series resistors affect the equivalent resistance?
I will refer to this annotated version of your circuit:
simulate this circuit – Schematic created using CircuitLab
If you look carefully, the top two resistors, R1 and R2 form a potential ...
- 47k
12
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How do I really calculate these resistors?
You have done the calculations correctly.
However, your biassing scheme will only work well with one set of transistor parameters, it's very sensitive to variations in beta. A better biassing scheme ...
- 174k
10
votes
Accepted
What is the maximum current of an electronic load?
The voltage and currents on the load have to be constrained within all limits simultaneously: -
Maximum current of 25 amps
Maximum voltage of 750 volts
Maximum product of voltage and current of 2400 ...
- 473k
10
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Does a resistor between two pairs of series resistors affect the equivalent resistance?
Your situation is a made trivial by its symmetry. My comment and the other answers point this out. Were it less trivial, a direct tool (with limited application) called the delta-wye conversion could ...
- 13.1k
9
votes
How do I really calculate these resistors?
You don't use that circuit in the real world....
Beta is horribly badly specified in real bipolar transistors (For example a random BC548 datasheet I just looked at give Hfe as 110 (min), 800(max), ...
- 17.6k
8
votes
Accepted
Clarifying an article on switch debouncing - something about leakage current causing trouble
Mr. Ganssle is saying that the worst-case leakage current (if it comes out of the input) multiplied by the R2 resistor value could result in the input voltage not getting close enough to ground when ...
7
votes
Time delayed deactivation of a circuit
I thought I'd provide both a thinking process and design procedure, given the lack of information about the current or voltage supply. But I won't provide any part selections or values since there are ...
- 78.7k
7
votes
Is voltage and current sources linear or nonlinear?
Only elements that have both inputs and outputs can be considered to be linear. "Linear" is a term that applies to a system with inputs and outputs, since it describes a particular kind of ...
- 478
7
votes
LEDs seem to automatically self-regulate to achieve ideal voltage across terminals
LEDs forward voltage and current are described in the I/V curve:
By limiting the current with the 50kOhm equivalent resistance, you probably put the LED in the region with about 3V of forward voltage ...
- 7,984
7
votes
Do higher voltages cause heating?
Why did the dryer overheat at the higher voltage
Ohm's law prevails in simple elemental components like a heater element and, ohm's law tells you that if you double the voltage, the current also ...
- 473k
7
votes
Does a resistor between two pairs of series resistors affect the equivalent resistance?
If the voltage source is 5V, then the voltage divider 2R+3R generates 3V at each side of the 1 Ohm Resistor.
There is no current flow possible, because the voltage difference between this two points ...
- 1,346
6
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Am I insane to question that only with a closed path can electrons move?
A concept that might help you is the transmission line concept. The idealized transmission line is one with a characteristic impedance, and a fixed delay. Think of the transmission line as a trace on ...
- 29.5k
6
votes
LEDs seem to automatically self-regulate to achieve ideal voltage across terminals
I created the "random I/V curve from the Internet" Wesley selected for his answer. I'm still working on it as the curves aren't quite correct for any particular family of LEDs but it's still useful ...
- 180k
5
votes
Flow of electricity. Need explanation
Conventional current is the total flow of charged carriers.
In an electrolyte, these are both positively and negatively charged ions. In a plasma, electrons and positively charged ions. In ice, it's ...
- 174k
5
votes
Accepted
Why is this two-inductor circuit first order?
Why is this two-inductor circuit first order?
Can you follow this argument: -
And clearly, this is a single order circuit.
since these inductors can't be combined in series or in parallel
Oh yes ...
- 473k
4
votes
Am I insane to question that only with a closed path can electrons move?
An antenna is an "open circuit" if you look at it closely. When talking about alternating current, particularly radio frequency AC, conductors are not idealized components but interact with their ...
- 41
4
votes
Accepted
How to find the value of alpha in this curcuit?
You have a \$9\:\text{A}\$ current source that leaves from the top end by only two paths and arrives to the bottom end via only two paths. You have two unknowns, \$\alpha\$ and \$I_x\$. So this feels ...
- 78.7k
4
votes
How is voltage divided between two reverse-biased ideal diodes?
In case of ideal diodes you can see them as open switches if reverse biased, since there is no leaking current and so on.
So there is no voltage at this point. Its floating.
- 464
4
votes
Accepted
Current going into the positive pole of a battery while discharging a capacitor
Yes, current will flow into the battery, and in a sense you are trying to charge the battery.
The possible danger is that the battery is not designed to be recharged, or that the value of \$R\$ is ...
- 31.7k
4
votes
Accepted
Is reactive power periodic in nature? What is the exact difference between active power, average power, and real power?
What is the exact difference between active power, average power, and
real power?
I think you're confusing reactive power with instantaneous reactive power, so let's clarofy the terminology.
...
- 1,019
4
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Synthesizing an impedance given by transfer function (poles/zeros) using a passive network
With Verbal Kint's contribution, I'll expand on thoughts behind my earlier comment(s).
Notes from: "A Practical Method of Designing RC Active Filters"
I want to start out by reflecting on ...
- 78.7k
4
votes
Accepted
How to write the equation for the input side of a JFET?
I do not understand how this equation came up
It's as easy as this: what ever voltage you have at the input with respect to 0 volts (\$V_i\$) must equal the voltage between gate and source (\$V_{GS}\$...
- 473k
Only top scored, non community-wiki answers of a minimum length are eligible