# PHYS 1120 / 2020 Midterm 2 Study Guide

**Voltage**

Voltage from a **point particle**:

Voltage from an **electric field**:

* The only distance Δd that matters is the distance that is **parallel to the electric field** *

How voltage is related to work/energy:

If you need to find a particle’s speed from its voltage or energy, use the work-energy theorem from Physics 1:

**Capacities**

For a parallel-plate capacitor, THE ONLY THING THAT CHANGES CAPACITANCE IS A CHANGE IN THE AREA OF THE PLATES OR THE DISTANCE BETWEEN THE PLATES!!!

A capacitor is related to the charge on its plates and the voltage between its plates by

* Q and V can change each other but they can’t change C!!! *

**Resistors + Simple Circuits**

Resistance of a resistor is determined by its length and cross-sectional area: