New answers tagged

1

For instance, why don't measure the ability to store something by the volume it takes so why not charge per unit volume. There is nothing wrong with you defining a parameter which is the "charge per unit volume" but after defining it then what are you going to do with it? So here you have a capacitor and its charge per unit volume is $3 \;\text{C ...


2

I understand that capacitance is the ability of a body to store an electrical charge and the formula is $C = {Q \over V}$ Perhaps you just need to top thinking of capacitance as that. "Capacitance" sounds like "capacity", which leads to an intuitive trap like this: If I have a basket with a capacity of 2 apples, then a basket with more capacity can ...


2

We Use $C=Q/V$ because those were useful things to measure. It's often easy to forget, but many of the equations we use are chosen because the work, and because other equations didn't work. Never underestimate that part of the reality. We don't use "charge per unit volume" because that number is not constant. You can charge a capacitor up without ...


3

This question appears to be a pseudo-duplicate on the Skeptics exchange, as pointed out by @CraigGidney. The highlights of the comments here and answer there appear to be that: 1) Yes, one could potentially accrue some electricity from soil. 2) No, it would not (ever) be sufficient to charge an iPhone, let alone 3 times. 3) In the comments here, "there ...


13

You can use a high vertical tube to store water in it (fill it from the bottom by pushing the water in) How much water can you store? It obviously depends on the pressure you apply to push it in. If you push harder, there will be more water stored. The tube is characterized not the amount of water, but by how easy it is to store the water. Its "capacity" ...


2

A capacitor is used to store energy in form of electric fields. This electric field is created by charges on plates of capacitor. So, basically you are storing charge on capacitors. Let someone ask you how much charge you can store in your capacitor.What would you reply? Clearly , you reply " I may store 1mC or 100mC, depending on Potential difference ...


4

Capacitance is "charge over voltage" – and one farad is "coulomb per volt" – because the capacity of capacitors (something that determines their "quality") is the ability to store a maximum charge on the plate ($+Q$ on one side, $-Q$ on the other side) given a fixed voltage. When you try to separate the charges, you unavoidably create electric fields ...


1

why would increasing voltage, while keeping charge constant, have any effect on the ability of a body to store charge. (1) Capacitors don't store charge, they store electrical energy. For a capacitor, it is understood that one plate has charge $Q$ while the other plate has charge $-Q$ so there is no net electric charge stored. (2) If you increase ...


1

A power station or generator is not the thing you are asking about here - Your main question is why 25kV is the output. When designing a power station an engineer tries to get the most power out of the system as possible for a given input of energy, or peak efficiency. After the generator distribution and use becomes the main concern. It tends to be the ...


0

The generators in power stations consist of coils rotation in a magnetic field produced by an electromagnet. Some of these electromagnets are energised by the generator itself but the larger generator have a smaller generator associated with them to provide the current which passes through the electromagnet. The induced voltage depends on the magnetic ...


1

Induction current and displacement current are similar though, but very different terms. Induction current is the normal electric current but displacement current is the term which is only defined by Maxwells' equations. Now generally capacitors have a dielectric material between the +ve and -ve plates. When the capacitor is charged, there exists a strong ...


0

You are correct about inserting lightbulbs at X and Y. The same current flows through each branch, so the lightbulbs will be equally bright. However, the question is not whether there is a difference in the currents flowing through X and Y, but whether, if you connect a wire between them, any current will flow through it. Your objection, of course, will ...


0

What is the difference between the potential difference and potential energy of an electron? If I understand your question right, these terms are describing the same thing - one is just in a "per charge" version. Electric potential energy $U_e$ is the potential energy associated with one spot in the circuit. Electric potential or just potential $V$ is ...


2

For copper the temperature coefficient of resistivity is $3.9\times 10^{-3} \text{K}^{-1} $ and the temperature coefficient of thermal linear expansion is $1.6\times 10^{-4} \text{K}^{-1} $. They differ by a factor of about 24 so a change in temperature will cause a bigger change in resistance than in the linear dimensions of copper. Resistance is given by ...


0

Since the current density varies with radius, you cannot choose a disc of radius $x$ as a surface element. What the integral do is to sum the current over all elements. This is only possible if the current over each element is well defined. When choosing an element of integration (area in your case) you have to choose one whose the physical quantity you are ...


0

The potentiometer is used to compare voltages by matching them. At the balancing point no current flows through a galavanometer between the potentiometer circuit and the test circuit, so it does not disturb the test circuit. The potentiometer is most sensitive when, at the balancing point, the slider or jockey is towards, but not too close to, the end of ...


0

Rheostats are typically used in the electricity lab to "build" an adjustable generator from a constant-voltage generator, e.g. in order to measure the current-voltage characteristics of a component.


0

The critical observation here is that before the magnet is introduced, there are equal numbers of oppositely charged ions moving in opposite directions, exerting no net force on the water around them. The magnet, however, will deflect a positive ion going one way in the same direction as it will deflect a negative ion going the other way. This produces a ...


0

If the wire has a non-zero resistivity, then there will be a finite resistance between the points $A$ and $B$, say $R_{AB}$. However, to determine the p.d. between these points you would have to know the resistance of the whole wire (or do you just mean that the wire between the points $A$ and $B$ has finite resistivity?), otherwise you can use Ohm's Law to ...


-1

The electron was the number of electron which has number of charge is $1.6\cdot10^{-18}\,$eV. As the electric field is the region in which charged particles experience the force to perpendicular direction between electrical poles.The moving ions consists of positive charge and negative charge therefore the cations and anions which can be moving ions in ...


2

Maybe it is worth bringing a comment into an answer: Batteries have protective circuits. The most basic safety device in a battery is a fuse that opens on high current. Some fuses open permanently and render the battery useless; others are more forgiving and reset. The positive thermal coefficient (PTC) is such a re-settable device that creates high ...


1

Perpetual motion machines utilizing permanent magnets exist, but they are perpetual only until the magnets become demagnetized. See the answers here. For the rotating ones, if one used a brush to generated triboelectricity, yes, magnetic energy will be turned into electric. An intermediate kinetic stage is necessary, because it is changing magnetic fields ...


0

A magnet has magnetic energy because of it position/orientation with respect to another magnet or an external magnetic field. Magnetic energy isn't an intrinsic property of the magnet itself but rather of the system of which the magnet is a part. Take a simple example of two permanent bar magnets separated by some small distance with their north poles near ...


2

This was actually considered under the Plowshare project The idea being to use an underground nuke to heat the surrounding rock and then run it like a geothermal resource. However, radiation problems.


2

As you say, the problem is confinement (aka containment) - fusion is relatively easy; controlled, useful fusion turns out to be incredibly difficult and expensive. So the easiest way to harness it, and the only technically and economically viable way (for decades from now, and possibly a century or more into the future), is to have a large fusion reactor in ...


2

a giant air tank. if the tank is large enough, we could set off a bomb inside without exceeding the containment strength of the perimeter, then harvest power from the increased pressure in the tank. i imagine making a large air-tight tank might be cost-prohibitive, although a 19 million cubic foot tank is already in use. perhaps we could build a ...


0

No... In a nuclear bomb, energy does not last long enough... For continuous power, simply not enough...... But it might be possible to power a satellite launch vehicle with a nuclear bomb... But hydrogen fuel cells have an excellent efficiency which (probably) makes it a better option... All in all, I would say no... Regards, Pradyoth Shandilya


3

Theoretically, yes. The problem is that there's no way to build a "small" thermonuclear warhead. Fusion isn't as simple as fission, the latter being as easy as smacking the right amount of Plutonium together. It is technically energetically favorable to fuse heavy isotopes of hydrogen into helium, but the conditions required to do so include giving the ...


0

PLEASE REFER THE FOLLOWING TEXT: http://ncertbooks.prashanthellina.com/class_12.Physics.PhysicsPartI/Chapter%202.pdf OR Inside a conductor, electrostatic field is zero "Consider a conductor, neutral or charged. There may also be an external electrostatic field. In the static situation, when there is no current inside or on the surface of the conductor, the ...


0

We need to distinguish between the electrostatic case and the case of a conductor which is part of a circuit. Say you take a length of wire and place it in an electric field so that the wire is parallel to the field. For some short period of time the external field will exist inside the wire and as a result some free electrons in the wire will move in ...


4

You are misunderstanding. ELECTROSTATIC FIELD inside aconductor is zero, not electric field. ELECTROSTATIC field means the electric field created by charges at rest.We can understand this property by considering a conducting slab placed in an external field E. We can argue that the electric field inside the conductor must be zero under the assumption that we ...


2

The reason is that all experiments known can be explained by having two types of electric charge. To distinguish between the two types of charge them it is necessary to introduce labels, conventionally the labels were taken be "positive" and "negative". Because of history, electrons are given the label "negative".


1

The battery is an energy source that supplies the electrical energy to the electrons in the conductors. There is no actual flow of electrons. It's the energy that is transferred. A conductor contains large no. of atoms tightly packed with plenty of availability of valence electrons that are ready to move out from the atom if you supply a little bit of ...


0

A filament of a light bulb can be thought of as being composed of a lattice of positive metal ions which are vibrating about fixed positions and a sea of mobile electrons which are responsible for the metal being an electrical conductor. With no external circuit present a chemical process within a battery moves mobile electrons within the battery to produce ...


0

I try to think of everything in terms of chemical potential. Many batteries utilize lithium ions to create a chemical gradient. This creates a driving force across the circuit, called voltage. Keep in mind that the electrons are not moving that quickly - it acts more as a wave travelling through. If you are interested, you can learn more about the actual ...


0

Okay, it's partially wrong. A battery is a device that maintains a constant potential difference between its terminals (generally through chemical stuff). Circuits are conductors. Conductors have electrons that can easily flow across their atoms. It's like conductors have a "sea" of electrons. The potential difference causes the circuit's electrons to move ...


0

When the battery is set up a chemical reaction which moves electrons from one terminal (which becomes the positive terminal) to the other (which becomes the negative terminal). Thus an electric field is set up inside the battery which applies a force on the electrons which are being moved by the chemical reaction. Eventually the electric field is large ...


2

How can you do that when Vs and Vd are two different parameters? One must keep track of the variables. The power delivered to a resistor is $$P_R = V_R \cdot I_R = V_R \left( \frac{V_R}{R} \right) = \frac{V^2_R}{R}$$ where I have subscripted the variables so it is clear that the voltage and current variables are the voltage across and current through ...


0

P = Vs I and P = Vd I , both are correct. Former means Power consumed by circuit and latter power consumed by different circuit components like wires. Or $V_{s} I = V_{1} I + V_{2} I ...... V_{n} I$ Where V1 and Vn are voltage across different circuit components. If you use $P_{s} = V_{s} I$ and $V_{s} = IR$ You get , $P_{s} = \frac{V_{s}^2}{R}$ which ...


1

Yeah, I had this confusion too. But know that$$P=\frac{v^2}{R}$$ for RESISTOR circuits only. Actually Power for any circuit is (Instantaneous power more precisely) $$P=VI$$ Here's how: We know that $P=\frac{dW}{dt}$ Lets first calculate dW. dW is the elemental amount amount of work done on elemental charge dQ in moving it through a potential difference of V ...


-1

I think that by Kirchhoff's voltage law the voltage drop $V_d$ must equal the supply voltage $V_s$. So $V_d=IR=V_s$ and hence the result.


0

I think the spark come because the potential difference between the switch gaps tend to be high enough for the air in the gap to ionise and the ion pairs formed(positive ions and electrons).However,just like in modern physics (discharge tube),the p.d z not enough to prevent recombination of the ions and as the ions collide to recombine,a spark z formed.This ...


1

The thickening of oobleck and similar materials is due to a phenomenon called dilatancy. This happens because shearing the suspension forces the water to flow at very high shear rates through the restricted gaps between the solid particles, and that requires a very high shear stress. However the water itself is not thickened in any way, and its electrical ...


3

While the other two answers are technically correct, they are not actually addressing the engineering aspects of what comprises a "good" capacitor. Ideal capacitors in parallel or series circuits lead to ideal capacitors of different value, i.e. there is no measurable "quality" difference - ideal is ideal. In reality, of course, there are no ideal ...


1

in terms of making a better capacitor that can store more charge would you use in series or in parallel? To be sure, capacitors don't (ordinarily) store charge, capacitors store energy, i.e., a 'charged' capacitor is electrically neutral. If, by better, you mean store more energy for a given voltage, then you want the combination of capacitors to be ...


0

If you want to store more charge (assuming you're not increasing the voltage) you want more capacitance. The way to do that is to put your two capacitors in parallel.$$C_{T}=C_{1}+C_{2}$$ If you think of each capacitor as pair of parallel you could imagine them in parallel as being side by side and effectively just adding the area of plates together to ...


0

A capacitor is meant to store charges. The ability to store how much charges is measured as the device's capacitance. It is related to the voltage across the capacitor plates and the charge on the plates: C=Q/V Consider a parallel plate capacitor as shown: Suppose initially the charge on the plate is zero. Now you connect it to an emf. The charges ...


-1

Regarding your first question, I suggest you look up "parallel plate capacitor" and see how the capacitance C relates to the inter-plate distance d. To say more would risk violating the homework policy. I cannot be sure what scenario your teacher was describing in which the voltage decreased. In order to determine exactly what occurs when the plates of a ...


0

You should understand that the battery source is not a supplier of electrons. The electrons are inside the metal. The physics of semi-conductors and metal conductors are a little different. Let's start with conductors. A conductor is characterized by the availability of free electrons within the metal if you supply a little energy to liberate it. They have ...


0

When the switch is closed the information is communicated to the whole circuit via electromagnetic waves at (less than) the speed of light. This means that an electric field, which the mobile charge carriers feel, is set up in the wires almost instantaneously. The movement of the mobile charge carriers is the electric current and that current exists in all ...



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