Prep.3 | Science | Electric and Magnetic Forces | Unit 2 - Lesson 3

شرح ساينس الصف الثالث الاعدادي لغات - الفصل الدراسي الاول شرح ساينس الثالث الاعدادي - ترم اول لينك جروب الواتساب https://whatsapp.com/channel/0029Vaed... لينك تليجرام https://t.me/mrahmedelbashagroup In This Part : Electromagnetism and Oersted's Discovery: The relationship between electricity and magnetism was first discovered by scientist Hans Oersted, who found that an electric current passing through a wire produces a magnetic field around it. This phenomenon is known as the magnetic effect of electric current. The Electromagnet: An electromagnet acts as a temporary magnet; it is constructed by winding a coil of insulated copper wire around a soft-iron core and connecting it to a battery. When electric current flows through the coil, it generates a magnetic field that magnetizes the iron core, allowing it to attract magnetic materials like iron filings or heavy scrap. Once the current is disconnected, it immediately loses its magnetism. Factors Affecting Electromagnet Strength: The magnetic strength of an electromagnet can be controlled and increased by increasing the number of coil turns, increasing the intensity of the electric current flowing through it, and using a soft-iron core. The Electric Motor: An electric motor converts electric energy into mechanical (kinetic) energy. Its structure includes a coil of insulated copper wire that is free to rotate between the poles of a strong permanent magnet, connected to a battery via a split-cylinder commutator and graphite brushes. When current flows, the magnetic field exerts forces on the coil, creating a "torque"—a rotational effect produced by two equal but opposite forces—that causes the motor coil to rotate. The Electric Generator (Dynamo): The electric generator operates on the reverse principle, converting mechanical (kinetic) energy into electric energy. When the generator's coil is mechanically rotated between the poles of a permanent magnet (using energy from sources like wind, waterfalls, or steam), it cuts the magnetic field lines, producing an electromotive force that generates an electric current. The intensity of this generated current can be increased by increasing the rotational speed of the coil or the magnetic field strength. Applications: Electric motors are found in household appliances like washing machines and fans, as well as in tools like the electric drill, where the rotational speed can be controlled for different tasks. Electric generators are used in power stations to produce electricity for cities, in bicycles (dynamos) to power lights without batteries, and as emergency generators during power outages. بالتوفيق مستر احمد الباشا