# Energy

## In-class Content

- Concept Map: VEUF (SGA - 20 min)
- Electrostatic Energy (kinesthetic - 20 min)

## Homework for Symmetries

- (EnergyGEM231)
Three charges are situated at the corners of a square (side $s$). Two have charge $-q$ and are located on opposite corners. The third has charge $+q$ and is opposite an empty corner.

How much work does it take to bring in another charge, $+q$, from far away and place it at the fourth corner?

How much work does it take to assemble the whole configuration of four charges?

- (SquareHoopGEM24)
Consider a square loop with each side length $a$ carrying a uniform linear charge density $\lambda$.

Find the electric field a distance $z$ above the center of the square. (You may start with the electric field due to a single finite line of charge).

Find the work needed to bring a charge in from infinity along the $z$-axis.