Electrical Circuits

Formulae you need to know

Formula Equation
Charge formula Q=It
Ohm's law V=IR
Power formulae P=IV=I2R=V2R
Resistors in series RT=R1+R2 
Resistors in parallel 1RT=1R1+1R2
Potential divider 1 V1=(R1R1+R2)VS
Potential divider 2 V1V2=R1R2

Potential Divider

A potential divider is a simple circuit with multiple resistors in series, where the voltage across the resistors is split proportional to the resistance.

Nested Circuits

A circuit with nested series or parallel parts to it can be simplified "from inside out", much like evaluating brackets in a mathematical expression.

Open Circuit

An open circuit is a circuit with an infinite resistance load connected to the power supply - which, in practice, means that the terminals of the power supply are not connnected.

Short Circuit

A short circuit is the opposite of an open circuit - it's where there the terminals of the power supply are connected with no resistance. In practice, this usually means the terminals are connected by a wire or other conductive material with negligible resistance.