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Lesson 1: DC Circuits

Lesson 1: DC Circuits

This lesson is intended as a revision of basic direct-current (DC) circuits

Video Tutorials

Basic circuits - water analogy

Ohm's law and power

It was discovered in the 19th century that certain materials (so-called ideal resistors) have a current through them I that is proportional to the potential difference (voltage) across them V. This is not a fundamental law of physics (like momentum conservation) but is an observed behavior which some materials roughly follow (like the friction law we covered earlier in the course).

This can be written down as I = V/R, where R is the resistance. This equation is called Ohm's law.

The power dissipated in an electrical component is given by P=VI - i.e. the potential difference times the current. Substitute Ohm's law into this and you get another occasionally useful equation:

P=V2R

Measuring Voltage and Current

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