Science: Physics books will need rewriting

Cambridge scientists have achieved an important breakthrough which could mean school physics books have to be updated. A century after the electron was discovered, they have created a quantum measure of electrical current - creating another equation, I=eF, which physics pupils will have to learn.

The achievement is expected to lead to the first standard definition of the charge on a single electron. It also has far-reaching implications for ultra-low power energy sources and self-regulating "smart" computer chips.

The breakthrough was made by physicists in the same Cambridge University laboratory where the electron was discovered by J J Thomson, 100 years ago this month.

Professor Michael Pepper and his team used high frequency soundwaves to trap and drag individual electrons, one by one, through a device called a "split-gate" that concentrates electrons into a narrow stream. The electrons are carried along in the troughs of the wave, emerging at the same frequency.

The team is now trying for the first time to establish a precise standard definition of the charge of a single electron. The method is to measure the current using standard instruments and then divide it by the frequency.