4
Smoke Detectors Two types ; Use of Photoelectric Effect Use of Ionising Radiation Amercium -241 in the form of Amercium Oxide which is a decay product of Plutonium 241. Plutonium 241 is formed inside reactors from Uranium 238. Half Life of 432 years and decays by emitting alpha and gamma rays.

Smoke Detectors Two types ; Use of Photoelectric Effect Use of Ionising Radiation Amercium -241 in the form of Amercium Oxide which is a decay product

Embed Size (px)

DESCRIPTION

How does it work The alpha particles ionise some of the oxygen and nitrogen atoms in the air. A voltage is applied across the plates and this causes the charged particles to be attracted to either the negative or positive plates. This current keeps the buzzer switched off.

Citation preview

Page 1: Smoke Detectors Two types ; Use of Photoelectric Effect Use of Ionising Radiation Amercium -241 in the form of Amercium Oxide which is a decay product

Smoke DetectorsTwo types ; Use of Photoelectric Effect

Use of Ionising Radiation

Amercium -241 in the form of Amercium Oxide which is a decay product of Plutonium 241.Plutonium 241 is formed inside reactors from Uranium 238.

Half Life of 432 years and decays by emitting alpha and gamma rays.

Page 2: Smoke Detectors Two types ; Use of Photoelectric Effect Use of Ionising Radiation Amercium -241 in the form of Amercium Oxide which is a decay product

Smoke Detectors 2 Cost $1500 per gram but this is enough for 3 million smoke detectors.

Page 3: Smoke Detectors Two types ; Use of Photoelectric Effect Use of Ionising Radiation Amercium -241 in the form of Amercium Oxide which is a decay product

How does it workThe alpha particles ionise some of the oxygen and nitrogen atoms in the air.A voltage is applied across the plates and this causes the charged particles to be attracted to either the negative or positive plates.

This current keeps the buzzer switched off.

Page 4: Smoke Detectors Two types ; Use of Photoelectric Effect Use of Ionising Radiation Amercium -241 in the form of Amercium Oxide which is a decay product

How does it work 2When smoke particles enter the chamber they attach to the ions and neutralise them. Some alpha particles are also absorbed by the smoke particles causing less ionisation of the air particles. The current flowing between the plates drops and the alarm then sounds.