An isotope of americium which emits alpha particles is used in smoke alarms. Alpha radiation ionises the air and this allows a small current to flow between two electrodes. Alpha is weakly penetrating so smoke stops it, the current drops and the alarm goes off.
Why do they use alpha in smoke alarms not beta?
Why do they use alpha in smoke alarms not beta or gamma? - Answers Alpha is used because it rarely effects our bodies from the outside. This is because it only travels approximately 5cm.
What is the role of alpha particles in smoke detectors?
Alpha particles in smoke detectors. Thus the alpha particles knock off an electron from the oxygen and nitrogen molecules resulting in negatively charged electrons and positively charged atoms. The negatively charge electrons are attracted to the positive electrode and the positively charged atoms to the negative electrode.
What element is used in smoke alarms?
An isotope of americium which emits alpha particles is used in smoke alarms. Alpha radiation ionises the air and this allows a small current to flow between two electrodes. Alpha is weakly penetrating so smoke stops it, the current drops and the alarm goes off.
How do radioactive smoke detectors work?
Smoke particles disrupt the low, steady electrical current produced by radioactive particles and trigger the detector's alarm. They react quickly to fires that give off little smoke. How are isotopes used in smoke alarms?
Do smoke detectors use alpha or beta?
Smoke detectors make use of the ionising properties of alpha particles. They contain an ionisation chamber which consists of a positive and negative electrode along with a very small amount of the radioisotope Americium-241.
Why is alpha particles used in smoke detectors and not beta or gamma?
Gammas are waaaay too penetrating and would leave the detector. Even multi-MeV alphas will not penetrate the layer of dead skin cells you have. So, as long as you don't inhale the smoke detector there are no bad health effects.
What type of radiation is used in smoke alarms?
Most smoke detectors use americium-241 as their source. Some early models used radium-226, and commercial smoke detectors and some residential units used nickel-63. The types of radiation from these sources cannot make anything else radioactive.
Why does alpha particles can safely be used in smoke detectors because they?
Alpha particles are very heavy and cannot travel very far. They can be shielded by a layer as thin as a layer of dead skin cells. Ionization smoke detectors have a small americium source encased in a layer of foil and ceramic, which stops the alpha particles from traveling outside of the smoke detector.
How is alpha radiation used?
Therapy that uses a radioactive substance that gives off a type of high-energy radiation called an alpha-particle to kill cancer cells. The radioactive substance is injected into a vein, travels through the blood, and collects in certain tissues in the body, such as areas of bone with cancer.
How do radioactive smoke alarms work?
Ionization chamber smoke detectors contain a small amount of americium-241, a radioactive material. Smoke particles disrupt the low, steady electrical current produced by radioactive particles and trigger the detector's alarm. They react quickly to fires that give off little smoke.
How does a smoke alarm work physics?
Alpha particles are easily absorbed. A household smoke alarm measures the movement of alpha particles across a small gap. If smoke enters the detector, it will absorb the alphas and the detector will measure a drop in the number getting across the gap. This drop in measurement will trigger the alarm to sound.
How does smoke detector work?
The short answer. Smoke alarms detect fires by sensing small particles in the air using a couple of different kinds of technologies. Once they detect those particles above a certain threshold, they signal the alarm to sound so that you and your family can get to safety and call 911. Smoke alarms save lives.
What is the alpha particle in smoke detectors?
An isotope of americium which emits alpha particles is used in smoke alarms. Alpha radiation ionises the air and this allows a small current to flow between two electrodes. Alpha is weakly penetrating so smoke stops it, the current drops and the alarm goes off. Click to see full answer.
What is the isotope of americium used in smoke detectors?
The isotope of americium used in smoke detectors is americium-241, which decays by α emission to neptunium-237 with a half-life of 432.2 years. When the smoke detector is new, it is close to 100% americium. After 30 years, about 4.7% of the americium atoms will have decayed to neptunium. Similar Asks.
What is the alpha particle in Americium 241?
The alpha particles emitted from the Americium-241 collide with the oxygen and nitrogen molecules in the air causing them to ionise. To ionise means to knock off electron/electrons from an atom. Also Know, what is alpha radiation used for? Alpha radiation is used to treat various forms of cancer.
What is the alpha source of a smoke detector?
Radioactive isotopes which emit alpha particles can be used in smoke detectors. The animation below shows a smoke detector with the radioisotope Americium 241 as the alpha source. Smoke detectors make use of the ionising properties of alpha particles. They contain an ionisation chamber which consists of a positive and negative electrode along ...
How does smoke detector current work?
When smoke enters the ionisation chamber the alpha particles collide with the smoke particles instead of the air particles. The collisions with smoke particles does not result in ionisation so the current drops.
What is the ionization chamber?
The ionisation chamber consists of open channels allowing the air form the room to flow through it. The alpha particles emitted from the Americium-241 collide with the oxygen and nitrogen molecules in the air causing them to ionise. To ionise means to knock off electron/electrons from an atom.
What is smoke detector?
Smoke detectors are either photoelectric, ionization chamber, or combination. In photoelectric a weak light beam is aimed at a photo receptor. A rapid change in received light intensity indicates smoke. In an ionization chamber a strongly ionizing medium is used to rip electrons off of smoke particles, thus ionizing them. The detector senses the ionized particles and triggers the alarm.
Why are alpha particles used?
The main reason that alpha particles are used is that they are strongly ionizing, because they are helium nuclei without any orbiting electrons; they will rip electrons off of any particles that they encounter, whereas gamma rays and beta particles will not.
How does a smoke alarm work?
The smoke alarm triggers when smoke breaks the constant flow of ions. Alpha particles are very heavy and cannot travel very far. They can be shielded by a layer as thin as a layer of dead skin cells. Ionization smoke detectors have a small americium source encased in a layer of foil and ceramic, which stops the alpha particles from traveling ...
How to use a smoke detector?
What You Can Do 1 Use a smoke detector in your home. It can save your life. 2 Never tamper with an ionization smoke detector. Never attempt to tamper with or remove the americium. 3 Replace the batteries. Replace the batteries in every smoke detector in your home twice a year. Most detectors are certified for a useful life of ten years. Check the expiration date on your smoke detector when you replace the batteries. 4 Throw away outdated ionization smoke detectors. Your community may have a separate recycling program for them.
What is the ionization of smoke detectors?
Ionization smoke detectors use americium as a source of alpha particles. Alpha particles from the americium source ionize air molecules. This makes some particles positively charged and some negatively charged. Two charged plates inside of the ionization smoke detector create a flow of positively and negatively charged ions.
What is the americium used for in a smoke detector?
Smoke detectors are common household items that keep you and your family safe by alerting you to smoke in your home. Ionization smoke detectors use a small amount of radioactive material, americium-241, to detect smoke. On this page: About Americium in Ionization Smoke Detectors. What you can do.
Is a smoke detector a radiation detector?
Because of this shielding, the smoke detector poses no radiation health risk when they are properly handled. There is no health threat from ionization smoke detectors as long as the detector is not damaged and used as directed. Do not tamper with your smoke detectors, as it could damage the shielding around the radioactive source inside of them.
