# Tagged Questions

37 views

### Back EMF & Current, how can we make I stable?

Lets assume we have a wire that has $10V$ across and $1$ $Amp$ flowing, now if this conductor is introduced to a changing magnetic field, $-EMF$ is induced, can we control our voltage to increase it ...
174 views

### How could electromagnetic waves propagate through space although they have no electrons?

How could electric fields in these waves propagate through space although in space there's no electrons for the electric field to be formed? is there another type of charged particles that carry the ...
46 views

### Resistance of a cylinder contacted by two smaller circular faces

Suppose we have a solid homogeneous cylinder with radius $a$, heigth $h$ and conductivity $\sigma$. The top and the bottom face is contacted with a smaller circular face with radius $b$. How can I ...
68 views

### In calculating resistivity of skin do I use the body's surface area?

Most of the resistance of the human body comes from the skin, as the interior of the body contains aqueous solutions that are good electrical conductors. For dry skin, the resistance between a ...
181 views

### Temperature and resistance?

Why does resistivity increase with temperature? The explanations I have heard so far are that increasing temperature increases vibrations in the lattice structure resulting in the number of ...
381 views

### Relation between complex dielectric constant and resistance

I am having a real hard time understanding how I reach the expression that relates resistance and $\varepsilon''$ as the complex part of the dielectric constant. I was trying to follow a clear and ...
103 views

### is there any relation between resistance and magnetism?

i was holding a resistance wire(insulated) coiled up and both of its ends were connected to a Ohm-meter it was showing 18 ohms while the circuit was on i pulled the coil from both ends and made that a ...
69 views

### In a non auto-ranging digital multimeter, what do the increasing numbers in the Ohm section represent?

For my science fair project I am measuring the resistance of nichrome wires under different conditions. I am using an Innova 3300 digital multimeter to measure the resistance. Other websites have told ...
141 views

### Traditional Kirchoff voltage law in AC circuit?

The traditional (not taking into account phasor addition or complex addition) application of Kirchoff Voltage law, i.e. $\Sigma\Delta V=0$ along a loop, does not work for AC circuits. We can sum the ...
696 views

### Power dissipated on internal resistance of short-circuited voltage source

Suppose we have a voltage source with an EMF of $\mathcal{E}$ and an internal resistance $R$. If we connect to it a perfect wire with zero resistance, we get a short circuit. The value of the current ...
70 views

### What exactly is resistance?

I am trying to teach myself about electricity and magnetism and I have a few questions about resistance. How does resistance of say a long wire compare to that of a a short wire? what about thick and ...
111 views

### Electric field and capacitance across a resistor

Using a simple lattice model of conduction, where electrons are accelerated by an electric field, and are slowed down by bumping into the lattice, you get the following equation for current density: ...
271 views

### Resistance of aluminium rectangular wire

I am working on upgrading an electromagnet design program. There are currently two types of wire used for the coil, circular and strip (read as: rectangular). The current algorithms in this program ...
84 views

### Does a battery in a vacuum produce a current?

I've always assumed that the strong resistance of air is the reason there is no flow of electrons between the terminals of a battery until a wire is connect. However, in a vacuum there is no resistive ...
116 views

### How to calculate resistance of bunches of wires

I figure that the resistance of multiple wires would work just like adding in parallel, a bunch of wires that is. But couldn't any wire just be viewed as a bunch of wires, albeit small ones? I know ...
384 views

### Question regarding inverse relation of resistance with area of cross section

It is said that resistance is inversely proportional to area of cross section. But greater area will have greater electric flux, and greater electric flux will have greater magnetic flux, and greater ...
402 views

### Non-conservative Electric Field

I was watching this video from Walter Lewin and while watching these two videos, I noticed there is a "contradiction" in what he is doing. All links direct you exactly to where he begins, so you don't ...
3k views

### Is it possible to mathematically derive the formula for resistance?

Resistance is given by $\rho L/A$, where $\rho$ is the material constant, $L$ is the length, and $A$ is the area. Is there any way that this can be derived mathematically, or is the only way ...
1k views

### Resistance between two points on a conducting surface

Suppose we have a cylindrical resistor, with resistance given by $R=\rho\cdot l/(\pi r^2)$ Let $d$ be the distance between two points in the interior of the resistor and let $r\gg d\gg l$. Ie. it is ...