Electromagnets

• Electromagnetism is due to the magnetic fields around electric currents.
• The fields can cause forces with other nearby magnets which can be used to make motors spin and loudspeakers produce sound.
• Electromagnetism is part of Physics (Single Science) focusing on Magnetism and electromagnetism.
• A simple electromagnet is made by coiling wire around an iron nail.
• The strength of the magnetic field is greater: closer to the wire if the current is increased.
• The field inside a solenoid is strong and uniform.
• Electromagnets are used in devices such as electric bells, and door locks that can be controlled remotely.
• An electromagnet is a magnet made by wrapping a coil of wire around an iron bar and passing an electric current through the coil.
• Solenoids consist of a wire coiled up into a spiral shape.
• A solenoid, shown here in cross section, has a stronger electromagnetic field than a single straight wire.
• When an electric current flows, the shape of the magnetic field is very similar to the field of a bar magnet.
• The iron core in an electromagnet increases the solenoid’s magnetic field strength.
• The small magnetic fields caused by the current in each coil add together to make a stronger overall magnetic field.
• An electromagnet is a device that uses electricity to create a magnetic field.
• The motor effect is the force exerted on a wire carrying a current in a magnetic field.
• Fleming’s left hand rule is a method used to determine the direction of force on a current-carrying wire.
• Electromagnets are used in motors and loudspeakers.
• Electromagnets are devices that use electromagnetism, which is the interaction between electricity and magnetism.
• The fields of electromagnetism can cause forces with other nearby magnets which can be used to make motors spin and loudspeakers produce sound.
• The motor effect is the force exerted on a wire carrying a current in a magnetic field.
• The force on a given length of wire in a magnetic field increases when the current in the wire increases and the strength of the magnetic field increases.
• For any given combination of current and magnetic field strength, the force is greatest when the direction of the current is 90° to the direction of the magnetic field.
• The force on a wire carrying a current in a magnetic field can be found using Fleming’s left hand rule.
• To find the direction of a motor effect force, hold your thumb, forefinger and second finger at right angles to each other: the forefinger is lined up with magnetic field lines pointing from north to south, the second finger is lined up with the current pointing from positive to negative, and the thumb shows the direction of the motor effect force on the conductor carrying the current.
• Electromagnets are caused by the magnetic fields around electric currents, which can cause forces with other nearby magnets that can be used to make motors spin and loudspeakers produce sound.
• The motor effect is a phenomenon where a coil of wire carrying a current in a magnetic field experiences a force that tends to make it rotate.
• Fleming’s left hand rule can be used to explain why the coil turns.
• An electric motor is an electrical device that uses direct current to produce a turning effect.
• In an electric motor, current in the left hand part of the coil causes a downward force, and current in the right hand part of the coil causes an upward force, causing the coil to rotate anticlockwise.
• A split ring commutator is part of a dc electric motor that reverses the direction of the current every half turn of the coil, changing the current direction every half turn.
• Once the conducting brushes reconnect with the commutator after a half turn, current flows in the opposite direction through the wire in the coil, causing the motor effect forces to continue to cause anticlockwise rotation of the coil.
• Electromagnets are used in loudspeakers and headphones to produce sound.
• The motor effect is used inside headphones, which contain small loudspeakers.
• Variations in an electric current cause variations in the magnetic field produced by an electromagnet.
• The electromagnetic field interacts with the permanent magnet generating a force, which pushes the cone outwards.
• The current is made to flow in the opposite direction.
• The direction of the electromagnetic field reverses.
• The force on the cone now pulls it back in.
• Repeatedly alternating the current direction makes the cone vibrate in and out.
• The cone vibrations cause pressure variations in the air, which are sound waves.