From 4a08f4b377567cdf67086567b416cd1bf510a3ae Mon Sep 17 00:00:00 2001 From: Folkert Kevelam Date: Tue, 17 Feb 2026 12:13:06 +0100 Subject: [PATCH] Update lecture notes EE1P1 --- Courses/EE1P1_Electricity_and_Magnetism.typ | 106 ++++++++++++++++++++ 1 file changed, 106 insertions(+) diff --git a/Courses/EE1P1_Electricity_and_Magnetism.typ b/Courses/EE1P1_Electricity_and_Magnetism.typ index 0966ce4..d42f968 100644 --- a/Courses/EE1P1_Electricity_and_Magnetism.typ +++ b/Courses/EE1P1_Electricity_and_Magnetism.typ @@ -62,3 +62,109 @@ === Spherical coordinates + EE1M1: $r, theta, phi$, EE1P1: $rho, phi, theta$ + += Lecture 2 + += Seminar 1 - Coulomb force + +== Coulomb force + +Force between two charges: + +$ + &arrow(F)_(S O)(arrow(r)_(S O), Q_S, Q_O) = k (Q_S Q_O) / r_(S O)^2 hat(r)_(S O) \ + &arrow(r)_(S O) = arrow(r)_O - arrow(r)_S \ + &r_(S O) = |arrow(r)_(S O)| = |arrow(r)_O - arrow(r)_S| \ + &hat(r)_(S O) = arrow(r)_(S O) / r_(S O) \ + &k = 10^(-7) c_o^2 approx 8.99 dot 10^9 "N sym.dot m" +$ + += Lecture 3 + +*polarisation* is when an electrical field is applied to a dielectric, which +causes the dipoles within the dielectric to orient to the same point, along +the external electric field. + += Lecture 4 - Gauss's law + +== Gauss's law in integral form + +Based on the idea of *flux*: + +- *flux* is the idea of how much of "something" crosses a given surface +- The *electrostatic field* does not cross anything (it was originally believed to) + +The electric flux can be calculated using the surface integral of the electric field. + +#definition[ + electric flux: + + $ + Phi = integral_cal(S) arrow(E) dot d arrow(A) = integral_S E cos(theta) d A + $ + + for a uniform field and a flat surface: + + $ + Phi = integral_cal(S) arrow(E) dot d arrow(A) = E A cos(theta) + $ +] + +#definition[ + Gauss's law: + + $ + integral.cont_cal(C) arrow(E) dot d arrow(A) = q_("enclosed") / epsilon_0 + $ + + Gauss's law in a medium: + + $ + integral.cont_cal(C) dot d arrow(A) = q_("enclosed") / (epsilon_0 epsilon_r) + $ +] + +assuming that homogenisation is applicable. \ +Gauss's law is useful for calculating the electric field in symmetric configurations: + +- spherical symmetry +- cylindrical symmetry +- symmetry with respect to a plane + +$ + arrow(E)(arrow(r)) = arrow(E)(r, theta, phi) \ + arrow(E)(arrow(r)) = E_r hat(r) \ +$ + +*Two distinct cases*: + ++ Observation point is inside the surface. + with a sphere, with a uniform charge density the total charge is: + $ + Q_("tot") = rho (4/3) pi R^3 + $ ++ Observation point is outside the surface. + + +=== Examples + +==== Calculating the electric field in a sphere with a single charge + +==== uniformly charged rod + + + +== Conditions at the surface of perfect conductors + +== Local form of Gauss's law + +- The function describing $arrow(E)$ is continuously differentiable. +- the medium can be taken as "continuous" (homogenisation). + +#definition[ + Gauss's law in local-form: + + $ + arrow(nabla) dot arrow(E)(arrow(r)) = rho(arrow(r)) / epsilon_0 + $ +]