# Questions tagged [electricity]

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

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11 views

### Charging by Touch

It is known that by maintaining contact between a charged body (let's assume it is negatively charged, a larger than usual number of electrons) and a neutral body, the neutral body acquires the same ...
19 views

### Why is potential difference across the ends of a conductor equal to the product of electric field and length of the conductor?

Why is the potential difference across the ends of a conductor equal to the product of the electric field and length of the conductor? Explain this considering I am in high school.
42 views

### Why is there an upper bound to the frequency at which an electronic device can be operated? [closed]

Why is there an upper bound to the frequency at which an electronic device can be operated? For example, the frequency of electricity that we receive at home is 60Hz (in the USA). What will happen if ...
27 views

### Difference between ions, free electrons, and excess charge

This part from University Physics turned my world upside down. What is the difference between ions, free electrons, and excess charge? Also, ions and free electrons make up a neutral conductor? Bloody ...
61 views

### Why is internal resistance of battery considered outside the terminals although it is present between the terminals inside the battery

In ideal battery the internal resistance is zero whereas in non-ideal battery there is some internal resistance now this internal resistance is due to the battery material (electrolyte) and is present ...
7 views

### Location of electrons in a charged object

When a material like glass or plastic becomes negatively charged by friction, or when a metal object like an electroscope armature is negatively charged by contact, do individual atoms in the material ...
41 views

### Why doesn't a chemical reaction occur with the movement of electrons in the context of electricity?

In school it is generally taught that the movement of electrons between two atoms causes a chemical reaction. However, when it comes to electricity why doesn't a chemical reaction occur with the ...
110 views

### What do $\ell$ and $A$ precisely mean in the formula for electrical resistance?

The formula for resistance is $$R=\rho\frac{\ell}{A}$$ Generally in most of the textbooks it simply written that $\ell$ is the length of the conductor and $A$ is it’s cross-sectional area. But my ...
2k views

### What does the notation $8.9875517923(14)$ mean? [duplicate]

The number $8.9875517923(14)$ appears in Coulomb's constant. I have read that it has something to do with the uncertainty of the accuracy of the number but answers have been unclear. Can somebody ...
28 views

### Bridge full wave rectifier more smooth signal [closed]

This is a full wave bridge rectifier: The waveform of the full wave bridge rectifier is this : But I want a more smooth signal which will remind less of an AC. If I put an inductor with a resistor ...
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### Explain electrostatic potential and similar terms? [closed]

How would you explain electrostatic potential, electrostatic potential energy, electrostatic potential difference, electrostatic potential gradient and common potential What is the difference between ...
30 views

### How does a dielectric form in an electrolytic capacitor?

I have found that this happens through anodic oxidation, but can't seem to find how this happens. Why do some metals form an insulating layer when in contact with an electrolyte?
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### Capacitance of ferroelectric capacitor in saturated regime

Consider a ferroelectric plate capacitor connected to an AC source in the presence of a strong static external electric field which sets the ferroelectric medium in the saturated regime. The question: ...
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### Why Ohm’s law doesn’t work in these scenarios (inside ideal battery and in vacuum)?

Scenario 1 - Ideal battery Suppose I have an ideal battery whose electrolyte’s resistance is zero. In the working battery there will be current flowing inside the battery also (due to battery forces) ...
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### What is the significance of direction of current density?

I studied about the direction of current density but nowhere it is mentioned that what is the significance of direction of current density Also I want to know why we used dot product instead of cross ...
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### In metals the conductivity decreases with increasing temperature?

I am currently studying Principles of Optics: Electromagnetic Theory of Propagation, Interference and Diffraction of Light, 7th edition, by Max Born and Emil Wolf. Chapter 1.1.2 Material equations ...
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### Is the secondary current in a transformer dependent upon the load resistance?

Is the secondary current in a transformer dependent upon the load resistance? If no, can we use a small(handheld) generator,with a step up transformer to power a house? Please give the mathematical ...
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### Basic Electrification problems

I am reading the experiments about Electrification in Part I Chapter I in "A Treatise on Electricity & Magnetism". There are few experiments on Electrification by friction, induction and ...
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### Persistent confusion about “electrons” in electricity

These two statements seems contrasting: Electrons in the outermost shell are loosely held to the nucleus. In a metal electrons move freely in all directions. I am very confused as to its position. ...
57 views

### Why does the power remain constant during the stepping up and stepping down of current in transformers?

I understand quite a bit of transformers, their structure and other concepts and formulas related to mutual induction. However I'm not able to explain why the electrical power has to be constant ...
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### Does increasing the electrode area of a battery increase the overpotential with the same current density?

I made a battery with an electrode area of 25 cm^2 and charged it at a current of 125 mA - giving a current density of 5 mA/cm^2. I made an identical battery but much larger electrode area - 350 cm^2 ...
8k views

### Is electricity really the flow of electrons or is it more involved?

I am new to the physics category of the Stack Exchange site. I apologize if my question is wrong, too broad, simple, or worded incorrectly. I am just trying to figure out what is true and false when ...
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### in photoelectric effect, where do electrons go when they are ejected from metal?

When light shines on a metal, electrons are ejected from the surface of the metal provided the energy of the photons are greater than the work function of the metal. My question is, (1) where do the ...
25 views

### Problem with ideal conductors [duplicate]

Let's assume we apply a potential difference or a battery accros an ideal conductor.Now as electric field across an conductor is zero potential from any end of the battery will never drop this is what ...
36 views

### Does the electron in wire too move because of voltage difference?

When we talk about electricity through a circuit because of a battery it is said that the electrons from negative terminal travel to positive terminal of the battery. I can't help but imagine about ...
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### What does the term 'high voltage' really mean?

This might be a dumb question but i am not so familiar with the word voltage: What does the textbooks really mean when they say high voltage?. Does that mean: There are more charges so more voltage, ...
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### Is there an expression for resistance in a circuit derived from Coulomb's Law?

Coulomb's Law states that the repelling force felt by two charges is proportional to the magnitude of their charges and inversely proportional to the square of the distance between them. Defining ...
656 views

### What's the point of an RMS value? [duplicate]

the RMS (root mean square) value of $f(x)$ is defined as: $$f(x)_{rms}=\sqrt{\frac{\int^b_a (f(x))^2dx}{b-a}}$$ Why do we do this very specific thing of taking the square, the mean, and then the ...
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### At what speed does electric information go?

Note: If a better title can be made, pls do so. Consider a parallel circuit with each branch of equal resistance. If you increase the resistance of the further branch, how long would it take to detect ...
45 views

### Why doesn't electric potential decrease gradually across a wire?

Let's assume that the resistance of a wire is zero. Now, suppose the wire has a length of 10 m and is connected to a battery with an emf of 10 V. According to my physics textbook, the electric field ...
22 views

### Is the path of an electron between successive collisions (with positive ions of the metal)a straight line in the presence of electric field?

I feel that the answer should be yes. While the entire journey isn't straight, the journey between successive collisions is straight. But the internet and my book says the opposite (the path is curved)...
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### Current flow in potentiometers

In the following circuit involving a potentiometer; Assume $V$ to be the voltage produced by the cell in the primary circuit across the length $AJ$ of the potentiometer wire, and $E$ to be that ...
36 views

### Electric Field Penetration through Multi-Layer Sandwiched Plates

I'm trying to understand how the total electric field changes as it passes through layers with different electrical permittivities and conductivities (as shown in the attached figure). The rectangular ...
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### Formal definition of charge density and current sources in classical electromagnetism

Charge density and current sources are fundamental to classical electromagnetism and appear in Maxwell's equations and everything that comes after. They are intuitive, charge density is a scalar field ...
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### How can opposite charges neutralize so fast?

I saw that the two end wires of a capacitor when touched to each other neutralizes quite fast(as the flash after their contact was there only for a second), how can charges neutralize the capacitor so ...
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### Why do electrodes have to touch initially in order to establish an arc?

In order to establish an arc in a low voltage, high current suruation such as welding, why do the wires or electrodes need to touch, then pull away to establish an arc? Why would this arc not be ...
104 views

### Why exactly do we feel a shock when we place our hand into a conducting solution?

I have a very naive question. Suppose you have pure water in a flask, and you place two ends of a copper wire (which are connected to a battery) into the water. If you were to place your hand into the ...
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### Charge distribution and electric field on a conductive sheet

I have a sheet of paper, clad with a half-circle shape of conductive material. The half circle is not filled to the center. The inner radius is about 8cm, and the outer radius about 12cm, not that the ...
26 views

### How much energy do I need to charge an electric car? [closed]

Suppose I have an electric car with a battery capacity of N kWh, how many kWh of power do I need to recharge it? It can't be a precise match of N - some must be lost through heat, powering the ...
31 views

### What does the voltage across a resitor tell you, and why does a voltmeter provide the voltage it does across multiple resistors in series?

In my physics class, we have begun talking about potential difference, charge, resistance etc. While watching online videos for extra help on some clarification, I often hear that as electrons move ...
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### Explanations for different current values inside a battery

I was just learning about what happens to current inside a battery, and my professor gave an example: Let's say we have a $1$ volt battery connected to a $1 \Omega$ load. Then he claimed that the ...
28 views

### Does electromagnet work without heat of wire?

If we isolate wire with thin wire and assuming that no heat rejected by wire then does electromagnet work. If it work then it violate conservation of energy .
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### Is there any relation between the torque required to rotate shaft of the alternator and the load connected to it?

Suppose that a TV and a LED bulb both could be operated by the electricity generated by the alternator. In the initial phase the LED bulb is connected to the alternator and then it is replaced by the ...
28 views

### Difference between heat emited from resistor and power on the resistor emited to heat

Consider a simple electric circuit. I just not understand what is the difference between heat emited from resistor and power that is on the resistor that emited to heat why one is $p=I^2R$ and the ...
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### Electric motor magnetic moment

Suppose I know that an electric motor winding produces 200 Nm torque in 0.2 T magnetic induction field. Is it possible to calculate the rotational magnetic moment produced by that motor winding just ...
41 views

### Is it possible to accelerate the air electrically?

Is it possible to accelerate the air electrically? There are other techniques such as, for example, compressors where the air can reach supersonic speeds. But is it possible to accelerate air to ...
19 views

### Decreasing of number of electrons in direction opposite to current [closed]

When a current is established in a wire,the free electrons drift in the direction opposite to the current.does the free electrons in the wire continuously decrease?
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### What will be the variation in potential in a zero resistance wire connected to a battery? [duplicate]

Consider an electric circuit with a battery and a resistor connected through a wire of zero resistance. Since the wire offers no resistance, all points on the wire are at same potential, then why on ...