Electricity & Magnetism

Electricity and Magnetism is a field in physics which looks at the effects on electricity and magnetics on the environment. This field is a major area of work with specialties being circuits, fields, charges, and waves and how they interact with electricity and magnetics.

Electricity is the set of physical phenomena associated with the presence and flow of electric charges. Electricity permits the creation and reception of electromagnetic radiation such as radio waves. Electricity produces electromagnetic fields which act on other charges. It can also occur in several different forms such as an electric charge, an electric current, electric field, electric potential and electromagnets.

Magnetism is a class of physical phenomena that includes forces exerted by magnets on other magnets. Magnetism originates in electric currents and the fundamental magnetic moments of elementary particles. Every material is influenced to some extend by a magnetic field. The magnetic state of a material depends on temperature so that a material may exhibit more than one form of magnetism.  

Categories within Electricity & Magnetism


Postings: 281

A charge is the physical property of matter that causes it to experience a force when close to other electrically charged matter.

Energy and Inductance

A. A long straight cable with radius R carriers a current uniformly distributed through its circular cross section. Find the self-inductance per unit length of the cable. Hint: find B inside and outside, then find energy everywhere and relate to the self-inductance (per unit length) B. This cable is now modified to have an in

B, H and M due to cylindrical conductor

An infinitely long solid cylindrical conductor of radius R carries a free current density J(s) = Cs^3z distributed over its cross section. The z axis is the long axis of the cylinder. The conductor has a permeability 'mu' which does not equal 'mu-0'. Outside the conductor is a vacuum. A. Find H, B, M inside the conductor and

Magnetic Field from Magnetic Vector Potential

A sphere is centered at the origin with radius 3m. It has a total charge of 100 micro-Coulombs spread uniformly over its surface and is spinning with 3600 revolutions per minute. 1. What is the magnitude and direction of the magnetic field inside the sphere? a. B=0 2. Given the magnetic vector potential (see in attachment),

Physcis 2

• Air in a cylinder is compressed to one-tenth of its original volume without change in temperature. What happens to its pressure? Imagine now that a valve is opened in order to restore the initial pressure value. What percentage of the molecules have escaped? • Consider a 40,000 km steel pipe in the shape of a ring that

Variation of J with r

Please see the attached question. I have to estimate the value of current density in terms of total current through the conductor.

Direction of magnetic field

Please see the attached question. I require an explanation about how the magnetic field depends on variation of current in 3D.

Non-uniform Surface Charge Density

I need some assistance in answering this question: A spherical shell of radius R centered at the origin has a surface charge density (file attached). 1. Setup the Coulomb integral for the electric potential V(z) for any point on the z axis. Find the function. 2. Evaluate V(z) at the origin (z=0) Note: you may need to look

Dipole, torque and force

Please assist with attached question about calculating torque and force on a dipole due to an external field. Thank you very much.

Interaction enrgy of dipoles

Please see question. More explanation about find the interaction energy: We have the distance given but not the direction. Need to find a general solution in terms of the angles formed by both dipoles.

Photodiode IV characteristics

Two p+-n abrupt junction diodes are made from silicon and are identical except that the donor levels in the 2 diodes are ND_1=10^15 and ND_2 = 1x10^17 cm-3. Sketch on one set of axes the I-V characteristics of the diodes for operation at room temperature. Label each curve. Also sketch on the same (or similar) axes the I-V cur

Derive magnetic field intensity due to a solenoid

Magnetic field is a vector quantity {vector B}, therefore, it has two components to represent it: Magnitude {B}, and direction. To find the direction, Right Hand Thumb Rule is used, while for magnitude, a basic law of Biot-Savart Law is used. Right Hand Thumb Rule [RHTR} states {in my words} that - if you are given a curre

thompson experiment, mangetic and electric field

I wonder how they can use (237) in (239) when (237) is without magnetic field and (239) is with both magnetic and electric field? The text is taken from this site http://farside.ph.utexas.edu/teaching/em/lectures/node33.html

Electron Density

Use the equation 9.1 to derive electron density( unit: electrons/cm^3) of polystyrene (C8H8)n and Lucite (C5O2H8)n. use the equ 9.2 calculate the Z/A ratio.

Electric and Magnetic Fields and Vectors

At one instant, the electric and magnetic fields at one point of an electromagnetic wave are : E = (220i + 300 j - 50 k) V/m and B = Bo(7.9 i - 7.9j + ak) muT 1. What is the value of a? 2. What is the value of Bo? 3. What is the Poynting vector at this time and position? Find t

Derivation of a Wave Equation about E,B & V,A.

1. Derive wave equation (about E, B ) by using Maxwell`s equations. 2. Derive wave equation (about vector potential, scalar potential) by using Maxwell`s equations. There are no conditions(such as no charges or no current) given, which means I have to solve in a general form! ***I am currently using Reitz's book<Foundat

Physics: Find the Poynting vector in vacuum and explain the result.

An infinite wire having current I oriented along z-axis passes through a small hole in a uniformly charged infinite plane at z = 0. The current is perpendicular to the charged plane (with charge density &#963;) . Find the Poynting vector in vacuum and explain the result.