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Physics module 5
Physice module 5
| Question | Answer |
|---|---|
| Electromagnetism | The movement of electrons in an electric current, which creates a magnetic field |
| Electromagnetic induction | A current that is induced to flow in a wire by moving the wire through a magnetic field or by moving a magnetic field through the wire, or by varying the strength of the magnetic field |
| Dipole | A tiny magnetic field created by a single spinning electron |
| Magnetic domain | A property of magnets in which the atoms in a small region are all aligned to produce a local magnetic field. |
| Magnetic field | The area around moving charged particles. It exerts a magnetic force on certain kinds of particles within the field. |
| One of three characteristics of the Magnetic field | The lines of force travel from the south pole to the north pole INSIDE the magnet and from the north pole to the south pole as curved lines in space OUTSIDE the magnet |
| Two of three characteristics of the Magnetic field | Lines of force in the same direction repel each other, and lines of force in opposing directions attract each other |
| Third characteristics of the Magnetic field | Magnetic fields are distorted by magnetic materials and unaffected by nonmagnetic materials. |
| Tesla | The SI unit (abbreviated as T) used to measure the strength of a magnetic field (1 Tesla = 10,000 Gauss) |
| Natural magnet | A permanent magnet, known as a lodestone; a rock with a natural magnetic force acquired from the earth's magnetic field. A lodestone remains magnetic unless something happens to change its alignment of electrons. |
| Artificial permanent magnet | A magnet that is manufactured. The manufacturing process turns an object into a magnet by inducing an alignment of atoms. |
| Electromagnet | An object that creates a temporary magnetic field through the flow of electricity. It has many applications in electric equipment. |
| Nonmagnetic | (i.e. glass, wood, plastic) These are not affected by magnetic fields |
| Diamagnetic | (i.e. water, mercury, gold) These are weakly repelled by magnetic fields |
| Paramagnetic | (i.e. platinum, gadolinium, aluminum) These are weakly attracted to magnetic fields |
| Ferromagnetic | (i.e. iron, cobalt, nickel) These are strongly attracted to magnets |
| Alignment | The spin of the electrons in the atoms is predominantly in the same direction. |
| Field of a positive charge | Points OUT from the charge |
| Field of a negative charge | Points INTO the charge |
| A stronger magnetic field will magnetize a ferromagnetic material more strongly. T or F? | True |
| According to the laws of magnetism, how will the north pole of one magnet react to the south pole of another magnet if placed very close together? | Attract |
| Magnetic flux travels from north to south inside a magnet. T or F? | False |
| Magnetism is defined by its ability to attract what? | Iron, cobalt and nickel. |
| Similar poles of magnets or similar charges of electric fields will what? | Repel |
| Water is magnetically classified as which of the following? | Diamagnetic |
| Lodestones fall under what type of magnet? | Natural magnets |
| Conductor | A metal or other substance with electrons that are free to produce a current |
| Solenoid | A device typically made by positioning an iron or steel core in the middle of a coil of wire, thereby increasing the strength of an electromagnet's magnetic field. |
| Polarity | A device typically made by positioning an iron or steel core in the middle of a coil of wire, thereby increasing the strength of an electromagnet's magnetic field. |
| Mutual induction | The phenomenon in which a current in one conductor induces a current to flow in another conductor |
| Self-induction | The process that occurs in a single coil of wire when an alternating current flows through it; the flow of electrons in one direction produces a magnetic field that induces a second current to flow in the wire, but in the opposite direction. |
| Lenz's law | The principle that an induced current flows in the opposite direction of the magnetic field change that induced it |
| Who is credited with establishing the principle of electromagnetism? | Oersted |
| the following describes four different coil. Which one, if moved through the magnetic field, would create the greatest voltage? 10 turns, 20 turns, 30 turns, 40 turns? | 40 turns. The greater the number of turns the greater the induced voltage. If you double the turns, you double the resultant voltage. |
| As a variation of the right-hand rule, if the right-hand rule is applied to a coil carrying current with the fingers pointed in the direction of current flow, what will the thumb indicate? | Direction of magnetic field |
| A coil of wire is being moved through a magnetic field. If the speed with which it is moved is doubled, what happens to the resulting voltage? | Doubles also |
| The indication of a "back" current within the same coil is called: | Self-induction |
| When a primary coil induces a current in a secondary coil, which of the following has occurred? | Mutual induction |
| What is the right-hand rule used to determine? | Direction of magnetic flux |
| Electric generator | A generator that produces an electric current by rotating loops of wire through a fixed magnetic field |
| Electric motor | A motor in which current is supplied to create a magnetic field around the coils, which are moved by the magnetic field of the stronger permanent magnets surrounding the coil. This motion makes the motor turn. |
| Transformer | A device that operates on the principle of electromagnetic mutual induction to change the electric potential to a higher or lower voltage and also raises or lowers the current. Transformers are used for this purpose in x-ray equipment circuitry |
| Armature | A coil of wire that rotates inside a magnetic field to produce an electric current. The more turns of wire in the coil, the higher the voltage induced in the wire. |
| Direct-current motor | A motor in which a commutator ring with rotating contacts or brushes reverses the current's direction in the coils as they rotate in the magnetic field of the permanent magnets. This ensures that the motor keeps turning in one direction. |
| Induction motor | An AC motor consisting of a rotor and stator. The electromagnets in the stator have a changing magnetic field that causes the rotor within to turn. |
| Step-up transformer | A device in the primary circuit that raises voltage to the kilovolt level needed to power the x-ray tube. A very high voltage is needed to produce x-rays. The primary coil is in the primary circuit; the secondary coil is in the secondary circuit. |
| Step-down transformer | A device included in the filament circuit to lower the voltage to the filament |
| Autotransformer | A device that raises or lowers voltage in the primary circuit, depending on the setting chosen on the machine's control panel for the kilovolt peak voltage (kVp) |
| Moving a conductor by manual means within a magnetic field is the basic operation of a: | Generator |
| The external magnets of an induction motor are called: | Stators |
| The commuter ring in a generator design briefly breaks contact between the armature and circuit. T or F? | True |
| Basic transformer operation is based on what principle? | Mutual induction |
| Which transformer design operates by self-induction? | Autotransformer |
| What is the fundamental design difference between a generator and motor? | Electricity is applied to the armature of a motor. |
| What is the unique electron characteristics of magnetic materials? | They all orbit in predominately one direction. |
| Lines of magnetic flux traveling in the same direction will attract each other. T or F? | False |
| An iron bar wrapped with a wire carrying electric current is what class of magnet? | Electromagnet |
| Platinum is magnetically classified as what? | Paramagnetic |
| Rubbing a ferromagnetic material against a permanent magnetic will magnetize that material. T or F? | True |
| Which scientist used a compass and a wire carrying electric current to demonstrate and study electromagnetism? | Oersted |
| Depending on the application of the right hand, the thumb can indicate either current flow or direction of the magnetic flow? | True |
| If the number of coils of a conductor is 40 and the voltage is 110, what will the voltage be if the number of coils is increased to 80? | 220 |
| The north and south ends of an electromagnet change each time an AC changes direction. T or F? | True |
| Which scientist formulated a law that explains a principle of electromagnetic induction? | Lenz |
| A simple generator will produce which current type? | AC |
| Converting mechanical energy to electrical energy is the purpose of which device? | Generator |
| A commutator ring in a generator design is attached to which of the following? | Armature |
| What causes the armature to rotate in a simple motor? | Two magnetic fields trying to align |
| In which device does a commutator ring serve to feed current through an armature the same direction each time? | Motor |
| The induction motor operates based on what principle? | Mutual induction |
| Transformers operate best with: | AC |
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