The document discusses Paschen's law, which determines the breakdown voltage required for electrical discharges between electrodes in a gas based on pressure and gap length. It highlights Paschen's contributions to physics and the characteristics of various gases such as helium and hydrogen when applying the law. Limitations of Paschen's law are also addressed, noting its dependence on the presence of seed electrons and the implications of external electron sources.

1. HIGH VOLTAGE
ENGINEERING
PASCHEN'S
LAW
IN SIMPLE
LAUNGUAGE
LEC # 08
BREAKDOWN
IN GASES

2. INTRODUCTION OF PASCHEN’S LAW
Louis Carl Heinrich
Friedrich Paschen
 Louis Carl Heinrich Friedrich
Paschen, was a German physicist,
known for his work on electrical
discharges.
 He is also known for the Paschen
series, a series of hydrogen spectral
lines in the infrared region that he first
observed in 1908.

3. PASCHEN'S LAW
Statement
 Paschen's law is an equation that gives the breakdown voltage (Vs),
that is, the voltage necessary to start a discharge or electric arc,
between two electrodes in a gas as a function of pressure (p) and
gap length (d).
 This equation is known as Paschen's law.
 The above equation shows that the sparking potential (V) is a
function of pressure (p) and gap length (d).
Vs = f(p.d)

4. PASCHEN'S LAW CHARACTERISCTICS
Study of a “PASCHEN’S LAW” Vs = f(pd)

5. PASCHEN'S LAW CHARACTERISCTICS
 Paschen’s curves obtained
for helium, neon, argon,
hydrogen and nitrogen.

6. LIMITATIONS OF PASCHEN’S LAW
Paschen's law requires that:
 There are already free electrons at the cathode, which can be accelerated to
trigger impact ionization. Such so-called seed electrons can be created by
ionization by cosmic x-ray background.
 The creation of further free electrons is only achieved by impact ionization.
Thus Paschen's law is not valid if there are external electron sources. This
can, for example, be a light source creating secondary electrons by the
photoelectric effect. This has to be considered in experiments.