A relay is an electromagnetic switch operated by a relatively small electric current that can turn on or off a much larger electric current.
How DC Motor works: The DC motor is a machine that transforms electric energy into mechanical energy in form of rotation.
A USB webcam is a camera that connects to a computer, usually through plugging it in to a USB port on the machine. The video is fed to the computer where a software application lets you view the pictures and also transfer them to the Internet.
A battery is a device consisting of one or more electrochemical cells with external connections for powering electrical devices such as flashlights, mobile phones, and electric cars.