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Electromagnet Notes 1. What is an electromagnet? - A temporary magnet made of a wire coil through which an electric current passes - How does it work? o History: In 1820, Hans Christian Oersted, a Danish Physics Teacher observed that the electrical current moving through a circuit moved the needle of a compass. When he reversed the current the needle was deflected in the opposite direction. When the current was cut off, the compass worked normally. Oersted hypothesized that the electrical current produced a magnetic field around the wire. Arrows show the direction of the magnetic field around the circuit Electric Current Design – By wrapping a wire around an iron core and attach the wires to an electrical source will produce a temporary magnetic field around the iron. To improve on this design one would need to either add more current to the wire and/or add more coils around the iron 2. Magnetism can be used to measure voltage and current: - Galvanometers use electromagnets to detect electrical currents o When current flows through the coil, the magnetic force causes the coil to rotate. The greater the current the greater the rotation. Attached to the coil is a needle and the movement is measured on a scale. 2 Types of galvanometers: 1. Ammeters – measure the electrical current passing through a circuit - Generally connected in series 2. Voltmeters – measure the potential difference of a circuit - Generally connected in parallel 3. In 1831 a British scientist, Michael Farraday and an American Scientist Joseph Henry found that by moving a wire through a magnetic field induced an electric current in that wire - This is known as Electromagnetic Induction - - o The process by which moving a wire through a magnetic field produces a current o Not only can magnetism be derived from electricity, electricity can be derived from magnetism. o What does this technology offer By using magnetic forces we can now utilize magnetism to power many household items How can we utilize electromagnetic induction in our homes o Electromagnetic induction is how a generator works!!!! o What is a generator? A device that produces an electric current by rotating a loop of wire in a magnetic field Or a device that uses electromagnetic induction to produce an electric current How is a generator different from an electric motor? o Generators use electromagnetic induction to produce electricity, while motors use electromagnetism to convert electricity into mechanical energy. Also the motor needs a commutator in order to function. o What is a commutator ? A reversing switch that causes the poles of the rotating electromagnet to switch Why would you want to switch the poles? The electromagnets turn the coils, if the poles of the temporary magnet do not switch when the north poles align with the south pole the coils would no longer turn Coil Commutator Brushes - Magnet