Deprecated: Methods with the same name as their class will not be constructors in a future version of PHP; plgContentJComments has a deprecated constructor in /var/www/astarmathsandphysics/plugins/content/jcomments/jcomments.php on line 25 Call Stack: 0.0001 360800 1. {main}() /var/www/astarmathsandphysics/index.php:0 0.0541 1209512 2. Joomla\CMS\Application\SiteApplication->execute() /var/www/astarmathsandphysics/index.php:49 0.0541 1209512 3. Joomla\CMS\Application\SiteApplication->doExecute() /var/www/astarmathsandphysics/libraries/src/Application/CMSApplication.php:267 0.1244 4190000 4. Joomla\CMS\Application\SiteApplication->dispatch() /var/www/astarmathsandphysics/libraries/src/Application/SiteApplication.php:233 0.1258 4217576 5. Joomla\CMS\Component\ComponentHelper::renderComponent() /var/www/astarmathsandphysics/libraries/src/Application/SiteApplication.php:194 0.1265 4235288 6. Joomla\CMS\Component\ComponentHelper::executeComponent() /var/www/astarmathsandphysics/libraries/src/Component/ComponentHelper.php:356 0.1267 4265808 7. require_once('/var/www/astarmathsandphysics/components/com_content/content.php') /var/www/astarmathsandphysics/libraries/src/Component/ComponentHelper.php:381 0.1276 4288528 8. ContentController->execute() /var/www/astarmathsandphysics/components/com_content/content.php:42 0.1276 4288528 9. ContentController->display() /var/www/astarmathsandphysics/libraries/src/MVC/Controller/BaseController.php:710 0.1794 4959808 10. ContentController->display() /var/www/astarmathsandphysics/components/com_content/controller.php:113 0.1830 5151960 11. Joomla\CMS\Cache\Controller\ViewController->get() /var/www/astarmathsandphysics/libraries/src/MVC/Controller/BaseController.php:663 0.1836 5172888 12. ContentViewArticle->display() /var/www/astarmathsandphysics/libraries/src/Cache/Controller/ViewController.php:102 0.1949 5377424 13. Joomla\CMS\Plugin\PluginHelper::importPlugin() /var/www/astarmathsandphysics/components/com_content/views/article/view.html.php:189 0.1949 5377680 14. Joomla\CMS\Plugin\PluginHelper::import() /var/www/astarmathsandphysics/libraries/src/Plugin/PluginHelper.php:182 Deprecated: Methods with the same name as their class will not be constructors in a future version of PHP; JCommentsACL has a deprecated constructor in /var/www/astarmathsandphysics/components/com_jcomments/classes/acl.php on line 17 Call Stack: 0.0001 360800 1. {main}() /var/www/astarmathsandphysics/index.php:0 0.0541 1209512 2. Joomla\CMS\Application\SiteApplication->execute() /var/www/astarmathsandphysics/index.php:49 0.0541 1209512 3. Joomla\CMS\Application\SiteApplication->doExecute() /var/www/astarmathsandphysics/libraries/src/Application/CMSApplication.php:267 0.1244 4190000 4. Joomla\CMS\Application\SiteApplication->dispatch() /var/www/astarmathsandphysics/libraries/src/Application/SiteApplication.php:233 0.1258 4217576 5. Joomla\CMS\Component\ComponentHelper::renderComponent() /var/www/astarmathsandphysics/libraries/src/Application/SiteApplication.php:194 0.1265 4235288 6. Joomla\CMS\Component\ComponentHelper::executeComponent() /var/www/astarmathsandphysics/libraries/src/Component/ComponentHelper.php:356 0.1267 4265808 7. require_once('/var/www/astarmathsandphysics/components/com_content/content.php') /var/www/astarmathsandphysics/libraries/src/Component/ComponentHelper.php:381 0.1276 4288528 8. ContentController->execute() /var/www/astarmathsandphysics/components/com_content/content.php:42 0.1276 4288528 9. ContentController->display() /var/www/astarmathsandphysics/libraries/src/MVC/Controller/BaseController.php:710 0.1794 4959808 10. ContentController->display() /var/www/astarmathsandphysics/components/com_content/controller.php:113 0.1830 5151960 11. Joomla\CMS\Cache\Controller\ViewController->get() /var/www/astarmathsandphysics/libraries/src/MVC/Controller/BaseController.php:663 0.1836 5172888 12. ContentViewArticle->display() /var/www/astarmathsandphysics/libraries/src/Cache/Controller/ViewController.php:102 0.4944 13793360 13. JEventDispatcher->trigger() /var/www/astarmathsandphysics/components/com_content/views/article/view.html.php:199 0.4946 13793760 14. plgContentJComments->update() /var/www/astarmathsandphysics/libraries/joomla/event/dispatcher.php:160 0.4946 13793760 15. plgContentJComments->onContentAfterDisplay() /var/www/astarmathsandphysics/libraries/joomla/event/event.php:70 0.4949 13802008 16. plgContentJComments->onAfterDisplayContent() /var/www/astarmathsandphysics/plugins/content/jcomments/jcomments.php:339 0.4951 13803744 17. JComments::show() /var/www/astarmathsandphysics/plugins/content/jcomments/jcomments.php:282 0.4957 13836792 18. JCommentsFactory::getACL() /var/www/astarmathsandphysics/components/com_jcomments/jcomments.php:188 0.4957 13837192 19. spl_autoload_call() /var/www/astarmathsandphysics/components/com_jcomments/classes/factory.php:274 0.4958 13837272 20. JLoader::load() /var/www/astarmathsandphysics/components/com_jcomments/classes/factory.php:274

Uses of Hard and Soft Magnetic Materials

Magnetic materials are classified as either hard or soft.

Soft magnetic materials are easily magnetised and demagnetised.

Hard magnetic materials are hard to magnetise, but once magnetised, they are hard to demagnetise.

Ordinary magnetics are made of hard magnetic material, since it is desired they retain their magnetism as long as possible. Until the early years of the twentieth century magnetic materials were made of steel containing between 1 % and 1.5 % carbon. It was later found that the addition of small amounts of other material – tungsten, chromium and cobalt – greatly improved the hardness of the steel. Research along the same lines led to the discovery of special alloys for making permanent magnets – alnico, alcomax and ticonal, which contain iron, nickel, cobalt and aluminium in various proportions.

Today a great range of permanent magnets of various types are used to make motors, dynamos and voltmeters, loudspeakers, ammeters, microphones. Conversely, it is often required to rapidly un - magnetise or re - magnetise a magnet. This is the case with electric door bells, relays, transformer cores. In these devices, soft magnetic materials such as mumetal (73% nickel, 22% iron, 5% copper) and stalloy (96% iron, 4%silicon) are used as well as soft iron.

Much research has also gone into sintered materials – the conversion of powdered materials into solid materials by the application of heat and pressure. Various very soft or very hard magnetic materials and some of the best permanent magnets may be made using this method.

Add comment

Security code
Refresh