What is the difference between a series circuit and a parallel circuit?

The fundamental difference between series and parallel circuits is essential for the CMEQ exam:

Series circuit:

• Current is the same through all components (I total = I1 = I2 = I3)
• Voltage divides: U total = U1 + U2 + U3
• Total resistance: R total = R1 + R2 + R3
• If one component fails, the whole circuit stops (e.g., Christmas lights)

Parallel circuit:

• Voltage is the same across all branches (U total = U1 = U2 = U3)
• Current divides: I total = I1 + I2 + I3
• Total resistance: 1/R total = 1/R1 + 1/R2 + 1/R3
• If one branch fails, the others keep working (e.g., wall receptacles)

Practical application: Lighting and receptacle circuits in a house are parallel. Switches are in series with the load they control.