Magnetism Flashcards
How does a compass work?
A tiny magnet is free to move and aligns itself with Earth’s magnetic field
Why is the earth’s geographic North really a South magnetic pole?
The North end of a magnet aligns with Earth’s geographic North, but is attracted to the unlike South magnetic pole
How does an electromagnet work?
Current through a wire produces a magnetic field. The magnetic field is stronger if the wire is made into a coil
What causes magnetism? Why are some materials magnetic and others not magnetic?
It caused by the motion of electrons. Materials, whose electron spins are balanced, are not magnetic. Materials, whose electron spins are unbalanced, are magnetic
What is electromagnetic induction?
A way to produce a voltage (emf) by moving a magnet near or in a coil of wire, or by moving a coil of wire in a magnetic field. It is the basis of how a generator works.
How does an electrical generator work?
It works by either moving a magnet near or within a coil of wire or by moving a coil of wire near or within a magnetic field.
Contract AC and DC generators.
AC generators maintain a constant connection with the coil of wire, resulting in electrons being forced back and forth as the magnet and/or coil move.
DC generators use a commutator to switch the connection to the coil every half cycle, resulting in electrons being forced being forced in the same direction as the magnet and/or coil move
How does a motor work?
A motor consists of permanent magnets and a coil of wire that acts as an electromagnet. Current is run through the coil, creating a magnetic field in the electromagnet that interacts with the field of the permanent magnet, causing the motor to turn from magnetic forces
Why is it necessary to reverse magnetic polarity to keep a motor spinning?
It must reverse every half cycle because the motor must alternate between attraction and repulsion of the magnetic fields in order to continue turning
How does a transformer work?
Two coils of wire are wrapped around a common iron core. Alternating current in the primary coil creates a changing magnetic field, which is carried through the iron core to the secondary coil. This changing magnetic field produces alternating current in the secondary coil. The ratio of voltages between primary and secondary coils equals the ratio of turns in the primary and secondary coils.
Describe an electromagnetic wave
An electromagnetic wave is a wave created by oscillating electric and magnetic fields that carries energy and can travel through empty space. These waves can travel through empty space at the speed of light, 3.00 x 10^8 m/s
Describe the electromagnetic spectrum in terms of the wavelength, frequency, and energy of waves.
Wavelength: 10^-12 m to 10^3 m
Frequency: 10^6 Hz to 10^20 Hz
Frequency and wavelength are inversely related, such that frequency times wavelength equals speed of light. Energy increases with frequency and decreases with wavelength.
State the names of waves in order starting from lowest frequency.
Radio (lowest frequency, lowest energy, longest wavelength), Microwave, Infrared, Visible, Ultraviolet, X-Rays, and Gamma Rays (shortest wavelength, highest frequency, highest energy)
