Questions tagged [physics]

Physics is the natural science that involves the study of matter and its motion through space and time.

Filter by
Sorted by
Tagged with
0
votes
2answers
54 views

What happens after disconnecting DC powered inductor?

Voltage over an inductor is proportional to the di/dt. I want to know what happens if I disconnect an inductor from a DC power suddenly. After disconnecting no current could pass through it, right? So ...
0
votes
3answers
111 views

How can a crossed dipole (turnstile) antenna be omnidirectional in 3D?

A crossed dipole or Turnstile antenna is said to not only be omnidirectional in the plane of the two dipoles, but its pattern is roughly spherical, there's no null along the axial (boresight) ...
2
votes
1answer
34 views

Crosstalk between transmission lines

I was reading these slides about crosstalk between transmission lines. At page 6 there is this circuital model to describe the effect of mutual coupling between these two lines: My doubt is: why \$I_{...
0
votes
1answer
57 views

How to analyze a capacitor connected to a DC voltage directly (no resistor)?

This may be a very basic question but my misunderstanding is due to the difference between how physics explains the charging of capacitors and how we analyze circuits in circuit analysis. According to ...
1
vote
1answer
28 views

Confusion on Voltage levels in Digital Waveforms

My question is why Io is in different direction when Vo=H and Vo=L respectively? I really can not understand the underlying mechanism!
2
votes
0answers
84 views

What is the noise electrical appliances / lights make before the power goes out during a blackout? [closed]

I have no prior EE experience, but I am curious about why there is a strange noise when a blackout occurs. It makes a high pitched noise right before the lights fade out? What causes incandescent ...
1
vote
0answers
27 views

How to calculate neutral base width for an emitter-base junction with forward bias voltage

I am trying to find the neutral base width for an emitter-base junction with a forward bias of 0.75V and a base-collector junction reverse bias of 20V. I am not sure how to factor in the forward bias ...
0
votes
3answers
52 views

How does being exposed to strong radiations effect nanosatellite electronics equipment?

I'm on paper designing a nanosatellite power system. The satellite would be orbiting in LEO. And I am wondering how and what type of radiation would affect its electronics. The system has a ...
-2
votes
2answers
112 views

Where does Ohm's Law, Kirchhoff circuit laws, etc, come from? [closed]

I know that these various laws that we use are often commonly accepted in practice but I am always curious how far down the rabbit hole you can do until you hit something that you just accept as true. ...
1
vote
1answer
69 views

Power calculation

Let's say I'm gonna charge a 1mF capacitor from 0 to 100V in 10 seconds. Assuming there's no limiting resistor nor any other losses, the total energy that must be tranfered from the 100VDC supply to ...
1
vote
1answer
54 views

Semiconductor diffusion current over time

Suppose you have an injection of holes into a semiconductor such that at some time you have this linear hole profile: Because the diffusion current at any point is proportional to the slope of P at ...
0
votes
0answers
41 views

Since current through capacitor (between the plates) is displacement current, what is the current flowing to the leads of a capacitor called?

Since there is no conduction current through the capacitor, what is the current that flows between the battery and the leads of the capacitor while the plates are charging (or discharging) to their ...
0
votes
2answers
59 views

How does writing a bit to a GPIO pin turn on my induction motor?

I have a Raspberry Pi 3 hooked up to a Yahboom 4wd robot controller board: When I set GPIO PIN 2 to output mode, then write a 1 to it, the fan turns on. What actually happens, physically, that turns ...
13
votes
9answers
4k views

Why doesn't higher frequency mean higher data rate?

My question is very primitive :) I've read multiple articles today and answers here, on Stack Exchange, but still don't understand one thing. Why doesn't frequency itself affect data rate in mobile ...
1
vote
2answers
95 views

How to automatically reverse the direction of a motor without human intervention?

I am working on this project where I have an arm at rest want a brushless DC motor (BLDC) to automatically reverse: (I've added an image and text above for a visual reference) Given that I am taking ...
1
vote
1answer
62 views

What is the length of one symbol sent through WiFI?

Having a WiFi emitter sending a frame, how much time does each symbol take? And therefore, what distance do they spread over? This depends on the Modulation Coding Scheme. I would like to know which ...
0
votes
0answers
24 views

Side lobe level of an aperture antenna

There is a electric field in the far zone of the rectangular aperture antenna as shown below. Antenna lies along the xy plane. $$E_{\theta}=\dfrac{jke^{-jkr}}{4\pi r}\dfrac{sin(0.5\lambda k sin\theta ...
1
vote
2answers
127 views

My oscilloscope tells me I vibrate at 60Hz. How?

As I live in North America, my initial hypothesis is that I'm picking the 60Hz from my house's power line. But, to my understanding, my body can't be a 60Hz antenna (1/4 wave antenna length for 60Hz ...
1
vote
4answers
63 views

Energy Transport in Circuits

I've been reading about how energy is actually transported in circuits (I first read about it here: http://amasci.com/miscon/ener1.html). The description in this article of why electrons don't move ...
0
votes
0answers
25 views

Temperature Effect on Schmitt Trigger Threshold Levels

I have found minimal information on the internet, as well as in multiple data sheets I have looked at. I'm designing for a large temperature range of 150°C. I require a fairly consistent voltage ...
1
vote
2answers
68 views

Transformer Secondary Discontinuity

I am using a step up transformer and I am getting a weird discontinuity in the secondary output. Has anyone seen anything like this before? I cant figure out what might cause this. In a one test setup ...
0
votes
0answers
17 views

How do i set up an offset antenna?

How do i set up an offset antenna? I have two offset antennas. 1 for receiving and the other one for transmitting, they are at the same altitude. I don't know how to set up the angle because the beam ...
0
votes
2answers
44 views

What is impeding current when voltage is stepped up in a transformer? [duplicate]

What is physically impeding electric current when a transformer steps up voltage? Is there some EM field along the conductor impeding electron movement? FYI, I'm not asking about losses or leakage. (...
0
votes
2answers
97 views

PN Junction paradox or something else? [duplicate]

[![I am having problem understanding reversed biased pn junction as the explaination provided by my book or any other source about flow of current in forward biased condition seems equally applicable ...
0
votes
3answers
214 views

Why should signals in circuits propagate much slower than the speed of light?

I've read a couple of other topics (such as this one and this one) about the lumped circuit abstraction requiring that signal timescales (i.e. the period of the highest frequency signal component) be ...
2
votes
1answer
62 views

reverse bias of the gate of an N-channel enhancement mosfet

So how negative can I drive the Vgs of an N-channel Mosfet before damage occurs? Datasheets specify BVDSS and BVGSS but these are "forward" breakdown voltages -- ie the absolute maximum Vds before ...
0
votes
1answer
127 views

Can anyone explain reverse bias pn junction using only electrons as charge carriers

In forward bias condition p-type semiconductor is connected to positive side and ntype semiconductor to negetive side and the electrons flow from n-type to p-type to cathode of battery. But imagine ...
2
votes
4answers
172 views

What is unit jω?

I have an equation, from which I'm calculating the induced voltage received by an RFID tag antenna. I know that \$ω\$ = angular velocity, but what is \$jω\$? And if \$jω\$ is related to angular ...
0
votes
0answers
43 views

Are there any general guidelines for knowing which order to find equivalent capacitances/resistances in

When simplifying a circuit with multiple capacitors or resistors is there a generally accepted order for knowing which equivalent capacitors/resistors to find first? Should I start farthest from the ...
0
votes
0answers
78 views

How to simulate a MMF fiber in COMSOL Multiphysics?

I am a complete newbie to COMSOL multiphysics, but I have to study and simulate the effects of temperature on multimode optical fibers (MMF) using COMSOL multiphysics for my Bachelor's thesis. I know ...
0
votes
2answers
39 views

Different ways or sensors to detect the weight on an object in a system

I am starting to gather information for a project I am excited about; my project is essentially a barbell that can detect the weight loaded on it. I will quickly summarize the function and restraints. ...
16
votes
5answers
2k views

Physics behind signal reflections and series termination

I have been looking for cause of signal reflections in transmission lines. Everywhere it is concluded that the reason is impedance mismatch. I can understand if the impedance changes in the path of ...
0
votes
1answer
47 views

Find electric field due to point charge +Q under given condition

As shown in the image, there are four conditions given: Electric field in figure:1 at point 'P' let = E_P, Electric field in figure:2 at point 'M' let = E_M, Electric field in figure:3 at point 'R' ...
0
votes
0answers
21 views

Error Propagation and Analysis on a experiment due to Voltmeter Constraints

I got a situation: at the moment I am unable to access both channels for Keithley 2182A nanovoltmeter using LabVIEW. However, for some odd reason, while I cannot access the channels at once, LabVIEW ...
0
votes
0answers
41 views

Transformer operating frequency clarification

I'm trying to design a small audio transformer. Specs are as follows: ...
0
votes
2answers
66 views

How can different voltages produce the same short circuit current?

I hope I’m not just thinking past something trivial but I can’t make sense of this. In this video, https://m.youtube.com/watch?v=XDf2nhfxVzg , variable voltages from .1-20V are used and when he shorts ...
0
votes
1answer
74 views

voltage potential energy clearance?

1 coulomb = charge of 6241509074460762607.776 protons(fixed amount of energy passing thru certain point). So 1 volt = 1 joule(energy) per 1 coulomb. and 2 volts = 2 joule(energy) per 1 coulomb. does ...
0
votes
1answer
59 views

Bidirectional level translator using N channel MOSFET

I'm using a n channel MOSFETa bidirectional level translator. The case when the body diode conducts the source end will be literally 0V or forward voltage of body diode, so the difference in voltage ...
0
votes
1answer
92 views

Is it logically explainable that current is lower when torque higher?

I am modelling a motor with a little simulation script. The principle is: Input is the traction force needed to be provided by the motor Output is the current to be provided to the coil of the motor (...
0
votes
0answers
39 views

Schottky diodes operation

As far as I know the depletion region is created due to the diffusion of majority charge carriers which expose the charge of their ions. Is this the same for Schottky diodes (electrons diffuse from ...
0
votes
2answers
143 views

How does the arc extinguisher work in a miniature circuit breaker?

In a miniature circuit breaker, as shown below, the distance between open contacts is much less than the distance between metal bars in the arc extinguisher part (the gap gets progressively longer ...
0
votes
0answers
54 views

Magnetic locks with paramagnetic materials

Well I was wondering why magnetic locks are made of an electromagnet and a ferromagnetic material and not an electromagnet and a paramagnetic material. The magnetic attraction between the ...
2
votes
5answers
93 views

Why is Frequency Conversion Additive in Acoustics Beating, but Multiplicative in Heterodyning?

In radio electronics, one of the first concept to learn is frequency conversion by using a mixer. And it's strongly emphasized that the mixer is a multiplier, not an adder used in audio circuitry. The ...
0
votes
1answer
71 views

Magnetic force and Coulomb force

Lets have 2 electrons travelling with some speed relative to a static observer. The force between those 2 electrons will be the Coulomb force and the magnetic force. Is it forbidden from the laws of ...
2
votes
1answer
54 views

Mechanical Circuit Analog Question

I'm doing a practice problem from https://6002.catsoop.org/F19/ex11/mechanical_analog The problem is as follows: A mass m = 10 kg is at rest on a horizontal plane with viscous friction coefficient B =...
2
votes
2answers
61 views

Magnetic force as a function of PWM frequency

Consider an experiement with a DC source feeding an coil with a constant DC current I. The coil with an iron core attracts a magnetic plate with mass m with force F. The force F is higher than Fm and ...
0
votes
1answer
650 views

Slayer exciter(Mini Tesla Coil) Not Working[IRFZ44N]

I made a tesla coil as https://www.youtube.com/watch?v=Ca2e3evwVK0 's circuit. the MOSFET seems to be getting hot and current passes through the primary but I get no response from the secondary. ...
0
votes
2answers
85 views

How to find the voltage of a capacitor in a Op-amp + RC network?

I found this practice problem online which asked to find the voltage across the capacitor as a function of time. The circuit is: My intended approach is to first find the initial condition when the ...
1
vote
1answer
118 views

Deep explanation on TVS diode voltage suppression?

I am looking for a deep explanation on why a TVS diode suppresses voltage. All of the research I have done on Google just says 'it suppresses voltage by shunting current', but this doesn't make sense ...
1
vote
1answer
52 views

Network Identification - How to find R1 and R2

I've been working on this practice problem I found online. So, from the graph I understand that \$R_{eq} = 2000\$ for the entire circuit. Since I want to find \$R_1\$ and \$R_2\$. To do this, I turn ...

1
2 3 4 5
7