Phys 122 - Direct Current Circuits

Based of Volume 2 of Physics for Engineers and Scientist 3rd Edition by Ohanian and Markert

What are the two kinds of currents?

AC and DC

How can we characterize the source of electrostatic potential in a circuit?

We call the electromotive force or emf

What is confusing about emf?

Emf is not a force, it is energy per charge, J/C, which can be considered voltage in our case.

What are common sources emf?

Batteries, Fuel Cells, Generators, and Solar Cells

What is important to know about current in a circuit?

In a closed loop the same current flows past any point.

Kirchoff’s Voltage Rule

All Emf’s added with potential changes must Equal 0.

What is power?

The rate at which work is done

Power

P = EMF of source * Current

Power Loss

P = Delta V*I = I²R=(DeltaV)²/R

Charge in a Capacitor in an RC circuit Charging

Q = CEpsilon(1-e^-t/(RC))

Current within an RC circuit Charging

I = (Epsilon/R)e^t/(RC)

Discharge of RC Capacitor

Q = CEpsilon(e^-t/RC)

Discharge Current

I = (Epsilon/R)^-t/RC