Shreyas’ Notes

Electricity and Magnetism

PHYS 102

spring, sophomore year

Electricity and magnetism are related to the existence and motion of electric charges.

e=1.6×1019Ce = 1.6 \times {10}^{-19} C

k=9×109N/C2k = 9 \times {10}^9 N/C^2

F1 on 2=kq1q2r2r^\vec F_{1 \text{ on } 2} = \frac{k q_1 q_2}{r^2} \hat{r}

F1 on 2=F2 on 1\vec F_{1 \text{ on } 2} = -\vec F_{2 \text{ on } 1}

FP=iFi on P=q0qfkqPr2dqr^\vec F_P = \sum_i \vec F_{i \text{ on }P} = \int_{q_0}^{q_f} \frac{k q_P}{r^2} \cdot dq \hat{r}

Law of conservation of charge: the amount of charge in a region cannot change except by charges flowing across the boundary of the region.

A flow of charges is called current.

Both insulators and conductors can be charged. When charges are placed on conductors, they repel each other and spread out to minimize electrostatic potential energy.

The electric field of a point charge qq is E=kqr2r^\vec E = \frac{kq}{r^2} \hat{r}. r^\hat{r} points from the point charge to the point of interest, and is placed at the point of interest. Electric fields exist regardless of the presence of a second charge.

F1 on 2=q2E1 at q2F_{1 \text{ on } 2} = q_2 \vec E_{1 \text{ at } q_2}