Electricity and Magnetism Answers

Calculate the number density of valence electrons in lithium given that the mass density is 530kg/m the molar mass is 7g/mol and that lithium is monovalent assuming that the mean free path of the electron in lithium is 1 nanometer calculate the resistivity of lithium at 295k

three equal point charges Q are arranged at the corners of a square of side L. draw the situation. what is the potential at the fourth corner, taking V=0 at a great distance?

Three narrow concentric rings of radii 50 mm, 70 mm, and
90 mm are centered about the origin, with the axis of symmetry of each ring oriented along the y axis. The charge on the inner ring is 1.0 mC, that on the middle ring is -2.0 mC, and that on the outer ring is 1.0 mC.
(a) What is the electric field magnitude at (0, 100 mm, 0)?
(b) What quantity of charge must be placed at (0, -100 mm, 0) to make the electric field magnitude zero at the position calculated in part a?

A permanent horseshoe magnet is mounted so that the magnetic field lines are vertical, as in the diagram below. If a student passes a straight wire between the poles in a horizontal plane and pulls it toward herself, (so in the diagram it would be coming out of the screen), the magnetic force is from right to left. Which is the north pole of the magnet?

An electron is moving through a magnetic field with a magnitude of 0.000045 T. If the electron is moving at a speed of 200,000 m/s, what is the magnetic force on the particle?

An X-ray machine emits electromagnetic photons carrying a frequency of 7.5x1017hz. What is is the approximate energy carried by each photon?

Assume theres a charge at point P outside a sphere of charge. How do we calculate the electric field at point P by treating the sphere of charge as a collection of thin disks of charge and without using Gauss's Law?

Obtain expressions for reflection and transmission amplitude coefficients when
electric vector associated with a plane monochromatic e. m. wave is in the plane of
incidence.

1. A 15 F capacitor is charged to 60 V and then disconnected from the battery. The plate
separation is then increased from 2.0 mm to 3.5 mm. calculate the amount of work
required to separate the plates. If the capacitor is submerged in distilled water, with a
dielectric constant of 80, determine;
a. the new capacitance, and
b. the potential difference across the capacitor.

Three charges Q1
= -2μC (0,0)cm, Q2
= 4 μC (0,10)cm
and Q3
= -3 μC (15,0)cm acts on one another. Find the
magnitude of the total electric force and the angle
that the total electric force makes with the positive
x-axis.