The kind of magic without which all of this wouldn't be possible. This tag should be used for questions about the **physics** of the fields that charged particles create and how these fields interact. It should not be used for all questions involving electromagnetism, that would be everything on ...

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3
votes
2answers
847 views

Skin depth at 50 Hz is much longer than the thickness of the shield of a coax cable. Then how does it work?

The title already narrates the question. We know that using a coax cable for audio amplifier input remarkably reduces 50 Hz noise. However the skin depth of the EM radiation at 50 Hz for copper is ...
0
votes
1answer
60 views

Solenoid circuit current issue

I have been working on a circuit go make a solenoid switch polarity with arduino. I originally used transistors (NPN) rated for 1A and 625mW in between the ends of the solenoid and ground. These all ...
0
votes
1answer
47 views

What is the difference between a magnetized nail and a coil?

When I was a child, I brought a nail (metal bar) and I made some turns around the nail. It was something like a coil and the nail was the core of that coil. When I applied DC on the coil using 1.5 V ...
-1
votes
3answers
83 views

Magnetic Field vs E-M Field

I have got some questions on this topic based on the best answers I get to these: -1- If magnetic fields arise due to electric currents in conductors, we say they are not E-M waves in nature; it is ...
0
votes
1answer
66 views

Why is there a copper winding isolated from the iron core of my transformer?

Here is a picture of a 1970's arc welding station. There is a 9 inch bar of metal surrounded by 88 windings of 4mm copper, that used to be on the end of the secondary winding, which is made up of ...
0
votes
1answer
44 views

magnetic flux cut by a magnet

I have two magnets A and B: Magnet A is movable, Magnet B is fixed. Magnet A is smaller and weaker (surface area of 1 Square cm) , where as magnet B is stronger and bigger (surface area of 4 Square ...
0
votes
1answer
30 views

What happens when I put a charge inside a conductor that is already in static equilibrium?

I understand how, when a neutral conductor is charged, the charges will repel each other and after the relaxation time will all be distributed in the surface of the conductor. My question is: after ...
0
votes
1answer
53 views

(theoretical) doubt in Gauss law [closed]

Let us assume the universe is filled with positive charges. At a particular point, all the positive charged particles will be symmetrical. Now, we assume a sphere of radius r (finite) as our Gaussian ...
1
vote
1answer
34 views

Clamp Meter Working Principle

Basic theory of clamp meter to measure rms of current wave. What I have in mind is that wire creates the changing flux that induces voltage in the meter.This voltage is calibrated ? Also how does the ...
0
votes
0answers
27 views

Generating current from a high voltage power line [duplicate]

I learnt that power lines carry high-voltage electric current with electric fields and a magnetic fields around them (That i just think go to waste). So i was asking, if i surrounded a single power ...
0
votes
2answers
49 views

Correct graph for induced E.M.F

Screen shot of the question is given below. What I know B field acting on the Ferris wheel is given below, And induced E.M.F initially is zero , therefore I can neglect answer number one and ...
1
vote
1answer
50 views

Findning the magnitude of the current

Screen shot of the question is given below. My thoughts Since the B field into the page is decreasing, and induced current is induced in such a way to oppose that condition. So here I can ...
-1
votes
2answers
31 views

How to determine the correct graph for induced current

To be straight , this is a home - work question . This is the question. Okay, now let me give you the my attempt and what I believe to be correct. Here E.M.F induced across OA is constant, ...
4
votes
1answer
73 views

How does a “neon tester” work?

I have seen the different answer posted in internet. Many people are saying glow of neon light on tester is due to stray capacitor formed by our body and ground. I am ok with that until I found ...
1
vote
2answers
195 views

How to choose the correct graph

This is a question based on electromagnetism. Screenshot of the question and all the necessary stuffs are given below, This is the figure , And the choices that are given, First choice ...
6
votes
1answer
137 views

Why does EM radiation travel much further than the magnetic field of an equivalent power electromagnet?

If both fall of as 1/r^2 from the source then why can radio waves travel around the world and still be picked up easily at the right frequency but the field from a powerful electromagnet can not?
0
votes
2answers
63 views

About induced current

This is a homework question that I have stuck for a while and couldn't able to come up with the correct answer. So here is the question, My thoughts towards this question When I move the rod PQ ...
0
votes
1answer
64 views

Direction of eddy current

To be honest, this is a homework question. Screenshot of it's given below. And the five choices are given below, What I already know I know that Eddy current is a circular electric which is ...
0
votes
1answer
45 views

Confusing transformer winding, what is it and can i change it?

here are two 380V to 24V/48v transformers that weigh 10 pounds each. I was hoping i could get 15V with 500w out of one at 240V and measure the welding potential. the secondary winding uses 0.5mm ...
3
votes
1answer
65 views

A doubt on electromagnetic induction?

First of all I have to admit that this is a homework question. Screenshot of it is given below, I am able to find only two things, and they are given below : Magnetic force acting on each frame ...
0
votes
0answers
44 views

What do we mean when we say that a quantity is phase wrapped?

I have asked a question here in researchgate and I'm looking forward to get the answer. I thought it might be helpful to post the question here in an electrical engineering Q&A site. please inform ...
1
vote
1answer
32 views

Phase angle and amplitude -

A plane electromagnetic wave has the shape: \$\vec{E}(\vec{r},t)=E_0\cdot cos(\vec{k}\vec{r}-\omega t)\cdot \vec{e}_y\$ \$\vec{B}(\vec{r},t)=(B_1\cdot cos(\vec{k}\vec{r}-\omega ...
2
votes
3answers
104 views

Doubt on induced voltage

Honestly, this is a homework question. Below you could see the description of the question Here you have the relevant answer. My argument Here we can neglect answer number 1 and 4 Reason : ...
0
votes
5answers
152 views

Does a coiled wire have a higher resistance than straight wire?

If you take a straight piece of wire that is insulated and coil it around a non ferrous object like piece of wood would the resistance change?
1
vote
3answers
52 views

BLDC max speed KV or Hz?

So from what I've understood, the KV rating for a motor gives us the rotor speed based on the voltage applied at the phase of the motor. Having looked a bit deeper in ESC / inverters, I've come up ...
1
vote
0answers
23 views

Question about transformer reflected source

The following show the idea how a Thevenin equivalent source is used to replace the primary circuit of transformer. In textbook it is commonly stated that the load impedance sees an equivalent ...
-2
votes
2answers
86 views

Periodicity of sinewave

I am studying about continuous time periodic signal in that I saw some examples of sine waves and I have a question. The example is \$sin(400 \pi t)\$ is periodic or not. The explanation is given that ...
0
votes
0answers
15 views

How to work out the magnetomotive force?

I don't know which formula to use for this past exam, there are so many. I was thinking of the formula: f = HL? But then I don't know the equation symbols for flux density and what a BH curve is. ...
0
votes
1answer
31 views

units of magnetizing force

In electromagnetic field theory, we talk about "magnetizing force". Units of magnetizing force is A/m (Amperes per meter). It's obvious that units of force is Newton. So, is amperes per meter equal to ...
1
vote
2answers
90 views

How do we model the behaviour of circuits on ultrashort time scales (< ns)?

The electric field has a finite propagation speed. How do we describe the behaviour of circuits on timescales before even changes in the electric field have reached the entire circuit? Is this is a ...
0
votes
1answer
43 views

permittivity and conductivity vs. attenuation [closed]

Is there any direct relationship between permittivity of a medium and attenuation of an EM wave? What about conductivity vs attenuation? edit: Ok for instance an EM wave traveling in sea water. I ...
-1
votes
1answer
51 views

What is a safe level of electromagnetic radiation measured in terms of received signal strength indicator (RSSI) e.g. -26 dBm?

We know that the laws of our countries set the regulatory limits of EM radiated power based on the EIRP transmit power of the antennas of devices. However, the received incident power is more ...
0
votes
1answer
59 views

Does circular motion of electron perpendicular to the magnetic field experiences a force?

If i am moving a charged particle in a circular motion and then applying the magnetic field perpendicular to this circular motion ,will the charge experience a force. Note that magnetic line produced ...
1
vote
2answers
59 views

Capacitance of a single charged plate?

Lets say we have a single plate that has a charge of +Q on it. A plate with charge -Q is infinite distance away. Will the plate with +Q have a capacitance associated with it? Why or why not? I was ...
0
votes
1answer
45 views

Difference in Lorentz force?

From the following diagram: Lorentz force can be calculated from the following formula: F = IL×B What about this wire in the following diagram? Assuming that all the variables are the ...
1
vote
1answer
74 views

Advantages of parallel over serial connections

As far as my understanding goes, parallel data connections are faster than serial at the same frequency. However, when you increase the frequency in parallel you start getting bits 'cross-talking' and ...
0
votes
3answers
71 views

Capacitor and inductor power factor

I need an explanation about the leading and lagging power factor at electron level. Case1: In a inductor it has the lot of free electrons are ready to move when we applied a voltage(AC or DC). If we ...
0
votes
1answer
45 views

Electromagnetic or microwave cooling

Heat means stored kinetic energy in matter. Microwave owens and induction heaters works on increasing kinetic energy on matter. Is it possible to make inverse of this heaters like cooler. We can ...
2
votes
2answers
68 views

PCB coil electromagnet driver

Based on external sensor inputs, I want to vertically pulldown & release (in a controlled manner) a 7mm neodymium magnet enclosed inside a circular elastic diaphragm. I want to keep the size as ...
0
votes
1answer
68 views

What is the importance of EM field theory in electrical engineering? [closed]

I am a student of electronics and instrumentation engineering and have a course of electromagnetic field theory in our semester. Though haven't gone so deep in subject but have some primary idea about ...
0
votes
0answers
26 views

Do RFID-shielding wallets protect against all variants of RFID coupling (even magnetic)?

I have been thinking about getting some kind of RFID-shielding wallet or a set of sleeves for some of my credit cards. Now from what I have seen there are different types of RFID coupling in use, ...
0
votes
1answer
26 views

Spice Simulation of EMI in Long Parallel Wires?

I was thinking about using an external power supply for multiple pieces of analog audio gear. But it occurs to me that even if I use separate grounds for power and signal, because the wires would run ...
4
votes
5answers
96 views

Nature of Electromagnetic Waves

We know that light is an electromagnetic wave. So is a radio frequency wave. From what I understand, the 50 Hz power frequency wave in our 230 V supply at home (60Hz and a lesser voltage in countries ...
1
vote
2answers
74 views

Regarding the forces created in magnetic field

This is a homework question of type multiple choices , question and 5 choices are given below. And a screenshot of the set up is given below. These are the things I know Forces are acting all ...
0
votes
1answer
48 views

How can a transistor be made smaller without changing the electric field?

Every time they introduce a new process node with reduced feature size, they tend to reduce the core voltage. The reason why is that the reduced size results in larger electric fields if they do not ...
0
votes
1answer
94 views

How do electric and magnetic fields affect electronic circuits?

I have come across those requirements: "The equipment shall not be susceptible to DC magnetic fields of up to 60 μT." "The equipment shall not be susceptible to electric fields of up to 140dBuV/m ...
0
votes
0answers
21 views

How to find Peak Electric and Magnetic fields of a Coaxial Cable?

By this I don't mean the simple statics problem. Lets say I have the power that'll flow through the cable, the frequency of the signal, and a standard data sheet for the cable, such as this one. How ...
0
votes
0answers
41 views

Battery life vs more power?

We are making in my intro to engineering class, an object that can travel about 20ft. We are only allowed a 1 AA 1.5v battery and motor. I was thinking we could trade battery life to increase the ...
6
votes
2answers
138 views

Intuitive explanation of Skin Effect?

I'm trying to wrap my head round Skin Depth, we've derived the wave equation from Maxwell's equations, using the conditions that it's a "good conductor" ρ = 0, σ >> ωε and ...
3
votes
2answers
145 views

How does a transformer transmit power from the primary to the secondary?

I'm trying to get my head wrapped around transformer operation and in the process regretting the times I snoozed in my Electromagnetics class as a EE student back when I was a lad :) I'm looking for ...