Electricity Definition and 999 Threads

Homework Statement Two pairs of charges are shown in Figure 1. Homework EquationsThe Attempt at a Solution I originally thought that the electric field past point 7 (i.e. points 8,9, 10) was the solution. However, this is wrong. I then considered point 1, yet that was wrong too. I even...

Homework Statement Homework Equations I = nqVA J = E/ρ J = I/A The Attempt at a Solution The underlying assumption was that current was constant across all 3 bits of the conductor, and thus answer is b. The concept I can't grasp is this: Why is current constant? Shouldn't a smaller A mean...

Homework Statement An infinite line charge (wire) has lambda = lambda0. It produces an electric field of magnitude 5E4 N/C at a distance of 2m. Determine the typical force between two adjacent extra electrons in the wireHomework Equations E_line = lambda/(2pi*r*epsilon0) The Attempt at a...

I saw strange flashes of light last night in a dark room and am wondering what caused them. They seemed the only happen when I moved the comforter, but it was not always in the same area. I thought at first it was a brief reflection of light, but I couldn't find a source for the reflection that...

Is electricity really the motion of electrons or charges? I'm kind of confused about the distinct differences. Any extra information would be greatly appreciated. I'd love to learn as much detail about this stuff as I can! Thank you!

Hey all, I've been thinking of a couple scenarios that involve thin wires (ones that have their diameter in the order of 1 mm). Suppose a gold wire with length L and diameter D is suspended straight in room temperature air and connected to some voltage V. Thus, a current will pass through the...

So I had a dream where I woke up in the bronze age. I wanted to create electricity (to impress the queen and that way I might be allowed into the royal castle to stay). So I researched and found Magnets are made of metals and an Electric Charge sent through the alloy of metals to create the...

It seems at first sight of the first circuit that all the resistors of resistance r are connected in parallel and i have thus simplified it to the second circuit. But then on numbering the nodes and redrawing the circuit i got the third circuit. I got the same equivalent resistance for all the...

Hi there, My name is Kathy and I am writing a book about the history of electrical discoveries. I am writing the book for adults who have limited (or no) science backgrounds with a lot of personal details (like Bose who liked to give electric kisses to attractive women, or Alexander Bell's...

I would generally avoid saying this, but it comes up a lot in the popular sites... What do people think? Bob

Homework Statement Homework EquationsThe Attempt at a Solution My thinking is that if the resistor's temp goes down then its resistance goes up. This means the current will bypass and ignore this resistor and the current around the circuit will stay the same? But this is wrong. The correct...

Is food waste attracted by the static electricity?

Hi, do you have any recommendations of books that deal with circuit analysis and circuit solving? I'm currently involved in a course that deals with linear circuits, and we are learning all of these methods of loop currents, thevenin's and norton's theorem, potential of knots and lots of methods...

Homework Statement A metal ball of radius ##a## is at a distance ##h>>a## from a very long conducting non-charged horizontal metal surface. Calculate the maximum electrical force on a ball under the condition that ##E_{cr}## the critical electric field of air is not breached. Homework Equations...

This is all related to GCSE content, but it doesn't go into enough depth for it to make sense: When a balloon sticks to a wall after becoming negatively charged, why does the surface of the wall become positively charged? I would assume that the repulsion between negative charges forces the...

1. Homework Statement A flat ring, with radii ##b>a## like on the picture is charged with a surface charge density ##ρ_s=ρ_0\frac{b}{r}## where ##ρ_0=const.## Calculate the potential of the ring on the ##z-axis## by taking the reference point to be in the infinity. Picture below. 2. Homework...

I have read that in 1729 Stephen Gray, in addition to generating static charges, sends, for the first time, electricity through a wire and coins the words insulator and conductor. What does he think he is sending though the wire, there is not yet a concept of atoms or electrons as we know them...

Homework Statement A very thin plane of length ##2a## is placed in the air at height ##a## above the conducting surface. The plane is charged on its surface and the expression for it's surface charge density (##ρ_s##) is given by ##ρ_s=ρ_{s0}*\frac{x}{a}## and ##ρ_{s0}## is some constant. a)...

I am working on "electrical energy" storage and I want to know why exactly can't we store "electricity" from a power plant. My understanding is that "electrical energy" storage actually refers to the conversion of electricity to other forms of potential energy (such as mechanical eg: dam, or...

Homework Statement Assuming the wires have negligible resistance, find the equivalent resistance between the terminals A and B. Answer to 2 significant figures. Homework Equations [/B] 1/R = 1/R1 + 1/R2 ... + 1/Rn R = R1 + R2 + RnThe Attempt at a Solution [/B] I have drawn a more...

Hi there, I am a teacher and will be teaching the topic of alternating current soon. I have not taught this before and have certainly not studied this in many years so I am trying to get a full understanding and am looking for a bit of clarification. So I know that the current supplied by the...

I'm a high school junior and doing a project on ben franklin. specifically I'm making a model of his electric motor which used two Leyden jars to operate. I want to make it a working model but I cannot get the leyden jars work. can anyone explain to me how to construct a historically accurate...

Dear all, I'n an EE that finished his degree more than 10 years ago. I wanted to refresh my Electricity and Magnetism knowledge. I bough Purcells book some weeks ago (https://www.amazon.com/dp/1107014026/?tag=pfamazon01-20) and I'm kind of struggling through the maths (Vector calculus). I've...

Homework Statement Write a program to find the equivalent resistance between two opposite corners within a grid of "infinite size" with resistors between each point. So basically we have an infinite cube made up of cubes with 1 ohm resistors between each node. Homework Equations Kirkoff's laws...

Recently I did an experiment where I dropped a magnet through a tube that was surrounded by a coil, and I hoped to investigate a factor that would affect the current induced (Faraday's law). I chose to study the effect that changing the cross-sectional area of the wire had on the induced...

Homework Statement A standard D cell can supply 10mA at 1.5 volts for about 300 hours. An alkaline D cell can do about the same. Assume - 2 - that the chemistry of the batteries will produce the same amount of energy and will maintain the same EMF regardless of the current drawn from the...

Homework Statement Determine Currents ##I_{1}, I_{2}, I_{3}## Homework Equations Kirchoff's Rules: $$\sum_{i=1}^n I_{i} = 0$$ $$\sum_{i=1}^n V_{i} = 0$$The Attempt at a Solution Basically, I'm not sure if I'm applying the Loop Law correctly. For example, in Loop A, going clockwise from...

Homework Statement Determine the resistance of wire at room temperature and at the melting point of the given material. GIVEN: Material = Aluminum Diameter of wire ##= 0.5 mm = 5.0 * 10^{-4} m## Length of wire ## = 0.5 m = 5.0 * 10^{-1} m## Temperature Coefficient: ##\alpha = 3.9 *...

hello, collegues, I need to calculate current on the right circuit, but I don't really know how. I have the current in left circuit I and L1 L2 C1 C2. I have tried to calculate this using impedance and ohms law. As Z2=Xc+XL, and U2=jwM, where M - mutual inductance I think that I2 should be...

I have a heat source in the form of a waste oil heater for a small workshop, i get around 200 degrees C from it and it warms the workshop up nicely. What i am wondering is is there a way i could produce enough electricty to run a small water pump from the excess heat? Something like a 12v pump...

Hi everyone, I'm struggling to understand what I think is a very basic concept: Joule's law of heating. Allow me to explain my confusion: We know that voltage can be expressed as: V = I · R And power can be expressed as: P = I · V Making power equivalent to: P = I2 · R According to my...

Why must steady currents be non-divergent in magnetostatics? Based on an article by Kirk T. McDonald (http://www.physics.princeton.edu/~mcdonald/examples/current.pdf), it appears that the answer is that by extrapolating the linear time dependence of the charge density from a constant divergence...

Let's say I have a spherically-uniform black-body radiator. It is losing energy, and therefore some of its mass, at a particular rate. From the frame of reference of the radiator, it has no momentum, but it has a changing amount of energy. From its frame of reference, the pressure on the...

Homework Statement Referencing the attached picture: a) Show that the RMS current in the 1 kΩ resistor is 6.5mA. b) If the AC voltage source was replaced by a battery, what would the current in the resistor be? Homework Equations V = IR Z = √(R^2 + X^2) The Attempt at a Solution To begin, I...

I just have a few conceptual questions: Is it as difficult to remove electrons from an insulator as it is to add to it? I understand insulators have a lower permittivity than conductors, and that they still allow charges to build upon the surface. However, I read that when you rub an insulator...

Homework Statement Find the voltage v and the currents i1 and i2 for the circuit below. Homework Equations V=IR The Attempt at a Solution I would combine the 10 ohm and 40 ohm, and the 18 ohm and 9 ohm, so that they are in series with the 6 ohm resistance. Then I would use V=IR to get the...

Homework Statement Design a voltage divider circuit to provide an output voltage v0 = 5V from a 12V source. The current taken from the 12V source is to be 100mA. a)Find the values of R1 and R2. b)Now suppose a load resistance of 200 ohms is connected across the output terminals (in parallel...

1) If I vary charge densities, but keep current density constant, do I get any sort of electromagnetic wave? 2) If the answer to question 1 is no, then if I vary charge densities, but keep current density constant, could I conceivably have a two isolated "open circuit" current elements of...

Let's say I have a disk magnet that is a centimeter thick and 1 meter in diameter. Now let's apply an external field confined to a cylinder of arbitrary position, angle, and length. Let's say it has a diameter of << 1 meter, so very, very narrow. Let's presume that the external field lines are...

Hi guys! For a school experiment we are supposed to connect a 9v battery to a 180 ohm resistor and multimeter and calculate how long it take to die at different temperatures . does anyone know how can i do this using a formula? I will need it in my report. Thanks for the help! :)

anorlunda submitted a new PF Insights post Ohm's Law Mellow Continue reading the Original PF Insights Post.

I heard that Griffith's Electrodynamics is at a similar level of Purcell's book on electricity; is it fine if someone goes into a graduate level electrodynamics book right after Purcell?

in my physics lab we did an expirement where we had to use an vernier electrostatic kit. So it consisted of placing a metal can inside a metal cage, and both were attached to an plastic disk, and below was a metal plate which was used for grounding. A black wire was connected from the cage to...

Homework Statement The conduction band of a metal is partially filled. When an electron of a metal from a lower band is excited and becomes mobile, the metal conducts electricity. The excitation also leaves behind a hole in the lower band. Q1. Does this hole contribute to the electrical...

sorry to post like this. if i need 220 v then how much electricity need?

Homework Statement Problem given in the image attached. Uniform Magnetic Field : B Positive Charge : q Uniform Velocity : v Mass : m Charged particle enters the magnetic field making an angle θ with the plane perpendicular to the magnetic field. Width of the region of Magnetic field : d d <...

Electrochemical hydrogen compressors (https://en.wikipedia.org/wiki/Electrochemical_hydrogen_compressor) basically convert an electrical potential difference into a pressure difference. Would it be possible to run one of these in reverse, i.e. using a pressure difference to create a voltage? If...

Hi PhysicsForums, I'm asking this as part of a small research project of mine in exploring hydrogen as an alternative energy source to fossil fuels. Based on my limited understanding, hydrogen is a good alternative to fossil fuels (especially in cars) because the only waste product is water...

How electricity passing through a conductor produces magnetic field around it. How an induction motor works. The energy or electricity which passes trough green earthing wire is transmitted into the ground. Why this energy is not conserved and can be used in future. All these three things are...

I read somewhere that conductors don't really store charge? How can this be correct? When a conductor is charged by conduction, the electrons spread throughout the surface of the conductor. Doesn't this mean that the capacitor is storing this electricity? What prevents conductors from being...