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# Physics Midterm/quiz

### physics notes

Question | Answer |
---|---|

What is the primary function of x-ray imaging systems? | To convert electric energy into electromagnetic energy |

Give an example of chemical energy? | car battery |

Give an example of electrical energy converted into mechanical energy? | Electric motor |

Give an example of electrical energy converted into thermal energy? | A toaster |

________________ are freely moveable? | Electrons |

Protons are more or less _________. | Fixed |

The total net charge of all matter in the universe is? | neutral |

An object is electrified when is has ________ or __________ electrons? | too few/too many (has a charge) |

What are the 5 laws of electrostatics? | Opposites attract/likes repel, Coulomb's Law, distribution, conductor, and movement |

What is Coulomb's Law? | Same as the Inverse Square Law, the intensity of radiation is equal to the source squared |

What is distribution with regards to the laws of electrostatics? | An electrical charge is distributed uniformly throughout or on the surface |

What is conductor with regards to the laws of electrostatics? | An electrical charge of a conductor is concentrated along the sharpest curvature of the surface |

What is movement with regards to the laws of electrostatics? | Only negative charges move along solid conductors |

Electrification can be created in 3 methods? | Friction, contact, or induction |

What is a electric ground? | Neutral objects p/u excess electrons from charged object |

Do positive electric charges move? | No |

What is a unit of electric charge? | Coulomb (C)1C = 6.3 X 10 to the 18th electron charge |

What is electric potential? | The difference in charge between two points. It represents the amount of work done to move charge from one point to another |

A unit of electric potential is measured in? | Volts |

Electric potential is also called? | Electromotive force (EMF) |

What is a conductor? | Any substance through which electrons flow easilyi.e. Copper |

What is an insultaor? | Any material that does not allow electron flowi.e. wood, rubber |

What is a semiconductor? | a material that sometimes acts like an insulator and sometimes like a conductori.e. water |

What is superconductivity? | The property of some materials to show no resistance below a critical tempi.e. MRI |

What is electricity? | Electrons in motion |

What is voltmeter? | measures potential difference between 2 circuit points |

A voltmeter is useful with a ____________ circuit? | parallel circuit |

What is ammeter? | measures current |

Ammeter is useful with a _________ circuit? | series circuit |

In a series circuit _____________ is constant. | current |

A series circuit | V=IRtotal R = R1 + R2 + R3total V = V1 + V2 + V3total I = I1 = I2 + I3 |

In a parallel circuit ______________ is constant. | voltage |

A parallel circuit | total V = V1 = V2 = V3total I = I1 + I2 + I3total R = 1/R1 + 1/R2 + 1/R3 |

What does an electric capacitor do? | It stores electric charge |

What is capacitance? | the amount of charges that can be stored |

What is a unit of capacitance? | farad |

Power is measured in? | watts |

Power formula | power = current X voltageP = IVpower = I2R |

Power loss increased with increased resistance? | Yes |

What is Lodestone? | A naturally occuring magnet(first used as a compass by Chinese) |

How is a magnetic field created? | when a charged particle is in motion |

The lines of a magnetic field are always ______ loops | closed |

A permanent magnet is usually made of what type of material? | ferromagnetic i.e. iron |

How are permanent magnets made? | by aligning magnetic domains |

What do electromagnets consist of? | a wire wrapped around an iron core, then an electric current is conducted through the wire |

How is a superconducting magnet made? | when a very large current is run through many loops of wire wrapped around a very large core of ferromagnetic material and wire is immersed in a helium bath |

What are diamagnetics? | Materials that are weakly repelled by the magnetic field |

What are ferromagnetics? | materials that are very strongly attracted to the magnetic field |

What is a photon? | atom of lightthe smallest quantity of any type of electromagnetic radiation |

What is field? | interaction among different energies, forces or masses that can otherwise be described as mathematically |

What is an electric field? | interaction of electrostatic charges |

What is a magnetic field? | interaction of magnetic poles |

What is amplitude? | area from crest to valley on the sine wave |

What is frequency? | # of cycles per second |

1 Hertz is equal to | 1 cycle per second |

What is wavelength? | the distance from one crest to another (side to side) |

The ___________ together the peaks, the ___________ the frequency? | closer/higher |

As the wavelength ___________________, the frequency ______________. | decreases/increases |

Wave equation: | Velocity = frequency X wavelength |

As the wavelength ________________, you have more crests. | decreases |

Frequency and wavelength are inversly proportional? True or false | True |

What is the difference between x-rays and gamma rays? | their sources |

What are the four fundamental fources of nature? | Gravity, Nuclear force, weak interaction, and electromagnetic force |

What did Hans Oersted do? | By placing a long straight wire next to a compass, when current passed thru wire, compass point turned toward wire, creting a magnetic field. Any charge in motion creates a magnetic field |

What is a solenoid? | a coil of wire (used as detent locks) |

What is an electromagnet? | a coil of wire wrapped around an iron core, which intensifies the magnetic field |

What is Faraday's Law | An electric current is induced to flow in a circuit if some part of that circuit is in a changing magnetic field |

The magnitude of induced current depends on the following? | 1. strength of the magnetic field2. velocity of the magnetic field as it moves past the conductor3. the angle of the conductor to the magnetic field4. the number of turns in the conductor |

What is Lenz's Law? | The induced current flows in a direction such that it opposes the action that induced it |

What are two types of induction? | Self and mutual induction |

What is self induction? | Induction of an opposing voltage in a single coil by its own changing agnetic field |

What is mutual induction? | Generation of an alternating current in a secondary coil by supplying an alternating current to the primary coil |

What is dipoles? | groups of atoms having electrons with magnetic moments in the same direction |

What laws do generators and motors use? | Oersted's and Faraday's Laws |

How can DC current be induced? | By using a commutator ring |

Electromagnetic radiation is inversly proportional to: | frequency and wave length |

Any charged particle in motion creates: | magnetic field |

The force of attraction between 2 opposite magnetic poles will be greater when poles are? | closer together and magnetic field strong |

The force that pushes the e- is? | potential difference |

The magnitude of an induced current depends on? | strength and velocity of magnetic field, angle of conductor, and # of turns in conductor |

What is the unit of frequency? | Hertz |

What is magnetic field strength measured in? | tesla |

The amount of voltage transmitted in a series circuit of 0.5A & 5 ohms would be? | 2.5V |

A series circuit has 3 resistors of 9, 10, and 16 ohms. If potential difference is 110V, what is resistance? | 35 ohm |

A series circuit has 3 resistors of 8, 12, & 15 ohms. If potential difference is 110V, what is total amperage? | 3.14A |