# Tagged Questions

The study of the presence and flow of electric charge. Charges, currents, fields, potentials.

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### Force on a magnetic dipole due to a magnetic field

Imagine a solenoid which has current $i$ and is producing a magnetic field $B$ which equals $$B=\mu N i$$ Now, imagine we put a small cylindrical magnet at the end of the solenoid. Then because at ...
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### Force Exerting on a magnetic train

A question is already asked ( How does this “simple” electric train work? ). But I've got a question about it. In order to calculate the force which is being exerted on the system including magnets ...
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### How do electrons choose their way through nodes? [duplicate]

Suppose I have a circuit, powered by some emf ($V$). If I put two resistors $R1$ and $R2$ of different resistances in parallel, the current at the node is divided following Kirchhoff's circuit laws. ...
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### Van der pauw method for an isolated hole

Van der pauw method is a way to measure the resistivity of a material with arbitrary shape while it meets some specifications ( being homogeneous and ...). One of the conditions is that the sample ...
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### Do we need wires for current conduction in ionosphere?

As we all know in ionosphere there are free ions and electrons present. So if we somehow take a bulb and a battery in the ionosphere then will the bulb glow due to conducting nature of environment ...
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### Electrons flowing through a circuit make it warm, where does that heat come from

in a circuit I have a low resistance device that consumes many watts, in normal operation this device will get warm; where does this heat come from? the law of conservation of energy states that the ...
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### How to figure out if an element in a circuit is absorbing or delivering power?

. Eg: In the above circuit. 50v source and 0.2Va current source is said to absorb power.If power is absorbed,what work is done with the absorbed power.
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### Which scientist is this?

Okay so I was watching discovery channel, in that i saw a man cleaning live electric wires of 10k volts in the air, he was not touching the ground. They said he was able to do this because of the "law"...
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### Charging by induction

When we charge an conductor by induction and grounding, we first bring a negative charge to the conductor. As a result the mobile electrons of the conductor get repelled and stay far from the negative ...
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### Electrical injuries - Doorknob vs powerline

This is something that has bothered me since high school physics. I have a medical and engineering degree, yet I can't for my life answer this question in a way that's logically consistent in my head....
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### What do we mean by live and neutral wire? [duplicate]

In our household circuit we have ac supply of 50 Hz. It means current reverse its direction in every 100th second. I think then, current flows in one direction then another.Then, why do we have live ...
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### What changes in the electrons before and after a voltage drop?

It is easy to visualize gravitational potential energy as a function of the position of height, and a change in this potential is manifested in a change in height. Further, by the work-energy theorem ...
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### The frequency induced by the alternating current

Let set up the experiment as followed. A string is stretched at two ends. Two magnet poles N and S are placed under and above the string. Now we let an alternating current go through the string with ...
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### Electric field along a wire and load

I have referred to many books and all of them apply loss in potential across a resistor only in case of circuits. However, the electric field is present in the whole conductor. Hence the electrons ...
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### Why does the metal mesh in an electric swatter make a whirring sound?

I have an electric bug swatter that operates on a rechargeable lead acid battery. I had one before that operated on disposable batteries and when it was turned on, it made a high pitched whining noise....
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### Physics Static Electricity [duplicate]

If a person has plastic soles, and are playing on Artificial grass and then the person touches metal goal post, the person will get a static shock.. Why?
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### What will be the effect on coulomb force if any conductor is placed between the electric charges?

I know that if any insulator or dielectric is placed between the electric charges then coulomb force decreases by factor known as dielectric constant.So, what will the effect when any conductor is ...
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### Experiment: releasing the copper bar above a permanent magnet

A classic experiment shows that when we drop a magnet through a copper coil long tube, there is eddy current induced in the coil. Then, due to lenz law, the motion of the magnet will be opposed and it ...
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### How exactly does a bulb light up?

A typical value for the electron drift velocity in a copper wire is $10^3\ \mathrm{m\ s^{-1}}$. In the circuit below, the length of the copper wire joining the negative terminal of the batter to the ...
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### Lightning sprites

Lightning usually occurs due to an electrostatic discharge between an electrically-charged cloud and the Earth's surface, or between clouds. There are also sprites, electrical discharges that occur ...
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### What is electric energy since electrons are not consumed?

I am interested in electronics as a hobby, so I have been reading up on the physics of electricity. I understand that difference in charge on battery terminals causes electrons to flow naturally ...
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### which is efficient on solar electricity by photo voltaic or thermal

As we know solar energy used to generate electricity in two major ways: photovoltaic and thermal energy. The most small applications or personal use are mostly using solar cells. But when it comes to ...
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### Can a floor made of copper pennies produce a static electric shock?

A friend is going to install thousands of pennies in a mosaic layout to be used as flooring in his home. Can this floor produce a static electric shock when walking on it? Is it possible to ...
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### Why don't you get electrocuted when you jump and touch an electric fence?

I've read that you won't get electrocuted if you jump and touch an electric fence because you aren't closing the circuit with the ground. Which is also why birds don't get electrocuted when they're ...
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### Will spinning DC motor in space generate infinite energy?

If I take a DC motor far in space and spin it, will it continue to spin forever and generate infinite electrical energy? If so, then won't it violate law of conservation of energy?
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### Is the electric field in the wires of the parallel circuit always the same and how that affects current?

When we connect two resistors connected in parallel with a battery, it creates an electric field through this wire. well, my question here: Is the electric field in the main wire is the same as the ...
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### Why does an electron lose all of its energy in a resistor?

Why does the electron uses nearly all of its energy for one resistor in a simple circuit made of a battery, wire, and resistor? I really need to know what happens exactly at the atomic level in the ...
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### Voltage and Current

I know that as voltage increases, current increases by $V=IR$, but I really find some difficulty in understanding this at the atomic level (what happens with the electrons inside that wire). I ...
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### Why is there an electric field in a wire even though it is a conductor?

If you take a perfect conductor, there cannot be a field across it since if there were, the particles would arrange themselves in a way to cancel out the field right? Yet, why does the same not hold ...
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### Why current of a battery drops continuously in high currents?

I have asked this question on EE SE but could not get a satisfactory enough answer. I have shorted an AA battery through an ammeter. Inititially, the current reading on ammeter was around 0.9 amperes ...
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### electricity and magnetism [duplicate]

A charge Q is distributed uniformly on the surface of a spherical conducting shell of radius 5 cm.The magnitude of electric field on the surface is 106 V/m. What is the magnitude of electric field20 ...
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### Corona discharge leading to hexagonal structure

Hexagons appear many times in nature, and I'd like to know why they appear in this situation too. Somebody has already been kind enough to help me figure out why this phenomenon occurs - it is due to ...
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### What is Electric-flux?

I've searched the question in the forum, and found the following conclusion : - "In electromagnetism, electric flux is the rate of flow of the electric field through a given area. Electric flux is ...
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### What would be the capacitance of an unequal charged capacitor?

I searched for this question but I cannot get satisfactory answer. Say if we have a parallel plate or cylindrical capacitor and if I supply unequal charge to it how could I find its Capacitance. We ...
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### How does electric potential relate to charge density in a wire?

Lets say we are talking about a wire with resistance connected to a battery. How is the charge density, taking into account bound and free charges, at two points connected to the electric potential ...
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### Why is electric flux zero if my point charge is outside of a sphere? [duplicate]

I am currently studying Gauss Law and Electric flux , during one of my exercises they ask me to find the electric flux of a sphere with radius 5 cm and my point charge is 10 cm to the left of the ...
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### Simulate Band Bending and Band Alignment in Semiconductors

Are there softwares (simple ones preferred) where we can simulate the band alignments and band bending of a p-n junction, where we can vary properties of the junction materials such as carrier ...
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### Comparison between current and voltage sensitivity

Current sensitivity of a galvanometer is defined as deflection per unit current, $$\frac{\phi}{I}=\frac{NAB}{k}$$ Here, $\phi$ is the angular deflection, k is the torsional constant of the spring, ...
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### Is there mechanical strain on a wire along the direction of current flow?

The (attractive) magnetic force on two parallel wires can be seen by the two wires bending towards each other. This can be explained by the Lorentz force acting on the charges and the charges "pulling"...
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### Why not run a cable from the north pole to the south pole to access its energy (magnetic or electrical)

Would a cable tied to the North Pole around the curve of earth downwards to the South Pole give us access to a HUGE AMOUNT of energy (magnetic or electrical) by linking into it.
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### Flow of electrons in an open circuit

In a closed circuit, electrons flow from negative electrode to positive electrode. In an open circuit, electrons only flow up to the end of the circuit. Why don't the electrons keep flowing into the ...
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### Conductive Rod in a Magnetic Field [closed]

I have a question about induction. Imagine a conductive object being moved in a magnetic field. What forces will it experience and how does the induced current in the object affect the motion, will ...
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### Why do electric pickles only glow at one end?

The electric pickle is often used as an example of a non-ohmic resistor. In the experiment, electric current excites the sodium ions inside pickle, producing very bright and intense light effect. What ...
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### Why does grounding yourself prevent feeling a static shock?

Sometimes I get static electric shocks when I touch certain metallic objects. However, I seem to be able to prevent this by grounding myself by first touching that object with a small piece of metal, ...
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Can we think that an ideal conductor is a friction less space for electrons since under influence of electric field they create an exactly opposing field and produce shielding effect ?If so then how ...
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### If I pass light through a conducting ring will I get an emf induced in the ring? Also if I do get an emf would that not violate energy conservation?

Here is what I think should happen. Light being an electromagnetic wave should have an oscillating magnetic component which should constantly change the flux linked with the conductor. Hence an emf ...
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### Attracting lightning with an ion beam

Can an ion beam be strong enough to create a path for lightning to travel to the ion machine? This is what I found in a lab that may help: An ionization factor jτi (the product of electron beam ...
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### Resistance used to get maximum illumination with proper security

In which way a resistance is to be connected with a bulb labelled 120V-60W when it is connected with 220V DC source so that maximum illumination with proper security is maintained? What is the ...