# About the music

Kraftwerk is a german band of musicians known to be pioneers of electonic music. The band was formed in 1969 and they were among the first to use synthetisers, drum machines and other computer-like instruments.

Radio-Activity is their fifth studio album released in 1975. It reached the first spot in France and is full of gems still very enjoyable now, like Geiger Counter and the eponym title Radio-Activity.

# About the science

Ohm ($\Omega$) is the unit of electrical resistance. It was named after XIX’s century german physicist Georg Ohm.

In the study of electrical networks, two quantities are very important:

• Electric current
• Voltage

Electric current (symbol $I$) is the flow of electric charges. An electric charge in an element can be a moving electon, or an ion, which is a whole molecule with extra (or deficit of electrons).

Voltage (symbol $U$) is a difference of electric potential energy between two points. Electric current can be measured at one point of a circuit when voltage needs to be measured between two points. It represents the work that has to be done to move the charge from one point to another, against the electric field.

Electric current is related to the number of charges moving and voltage is related to their force. However, faster moving charges will create a bigger flow and is related to the force as well. Thus the Ohm’s law explains the link between voltage and electric current in a circuit: they are proportional one of the other, and the constant $R$ of proportionality is a parameter of the circuit, it is called resistance.

$$U = RI$$