# Physics Week 24: Introduction to dc circuit analysis

The main topics covered during week 24 in the Physics course from the Ron Paul Curriculum were: EMF, terminal voltage, resistors, resistance circuits, and Kirchhoff’s law.

Lesson 1:

EMF: something that producing energy and an electromotive force

Resistors in Series: in a series circuit the total resistance is equal to the sum of the individual resistances.

Series circuit rules:

• The current is the same throughout the “loop”
• The voltage across each component (resistor) must add up to the same magnitude as the voltage source.

Resistors in Parallel: The reciprocal of the total resistance is equal to the sum individual resistances reciprocals

Lesson 2:

Practice problems

Lesson 3:

Circuit analysis: Kirchhoff’s laws are used to analyze complex circuits

Kirchhoff’s Laws:

• Junction Rule – based on the fundamental law, conservation of charge
• Loop Rule – based on the fundamental law, conservation of energy

Diagrams:

Problem solving steps:

• Label the currents
• Identify the unknowns
• Apply Kirchhoff’s junction rule
• Apply Kirchhoff’s loop rule
• Solve the equation for the unknowns

Lesson 4:

EMF’s in Series: The total voltage is the algebraic sum of their voltages

EMF’s in Parallel: EMF sources in parallel do not increase voltage, rather they are connected in parallel to reduce the amount of current each source must produce.