There are many cloud voting systems available which can be used in the classroom where wifi is available. The students can use smartphones, tablets or laptops which have access online. UvA has a license for cloud voting system Shakespeak (http://www.shakespeak.com ).
Faculty of Science staff can reserve free Shakespeak sessions for unlimited number of students: reservation form
There are many other cloud voting systems availabe, most of them are partly (or with a limited number of participants) free to use, for example
Original author: Natasa Brouwer