Ionisation
When an atom loses an electron, it lacks a negative charge and is therefore positive. An atom with a deficiency of one or more electrons is called a positive ion. On the other hand if an atom were to gain an electron, albeit temporarily, it is a negative ion.
In most metals the atoms are constantly losing and regaining free electrons. They may be thought of as constantly undergoing ionisation. Because of this, metals are usually good electrical conductors.
Atoms in a gas are not normally ionised to any great extent, and therefore a gas is not a good conductor under low electric pressures. However, if the emf is increased across an area in which gas atoms are present, some of the outer orbiting electrons of the gas atoms will be attracted to the positive terminal of the source of emf and the remainder of the atom will be attracted toward the negative. When pressure increases enough, one or more free electrons may be torn from the atoms. The atoms are ionised. If ionisation happens to enough of the atoms in the gas, a current flows through the gas. For any particular gas at any particular pressure, there is a certain voltage value that will produce ionisation. Below this value, the number of ionised atoms is small. Above the critical value more atoms are ionised, producing greater current flow, which tends to hold the voltage across the gas at a constant value. In an ionised condition the gas acts as an electric conductor.
Examples of ionisation of gases are lightning, neon lights, and fluorescent lights. Ionisation plays an important part in electronics and radio
When an atom loses an electron, it lacks a negative charge and is therefore positive. An atom with a deficiency of one or more electrons is called a positive ion. On the other hand if an atom were to gain an electron, albeit temporarily, it is a negative ion.
In most metals the atoms are constantly losing and regaining free electrons. They may be thought of as constantly undergoing ionisation. Because of this, metals are usually good electrical conductors.
Atoms in a gas are not normally ionised to any great extent, and therefore a gas is not a good conductor under low electric pressures. However, if the emf is increased across an area in which gas atoms are present, some of the outer orbiting electrons of the gas atoms will be attracted to the positive terminal of the source of emf and the remainder of the atom will be attracted toward the negative. When pressure increases enough, one or more free electrons may be torn from the atoms. The atoms are ionised. If ionisation happens to enough of the atoms in the gas, a current flows through the gas. For any particular gas at any particular pressure, there is a certain voltage value that will produce ionisation. Below this value, the number of ionised atoms is small. Above the critical value more atoms are ionised, producing greater current flow, which tends to hold the voltage across the gas at a constant value. In an ionised condition the gas acts as an electric conductor.
Examples of ionisation of gases are lightning, neon lights, and fluorescent lights. Ionisation plays an important part in electronics and radio
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