MIT 211 Lab Week 2 (questions about relationships for formulas lol)

What is the first law of electrostatics?

Unlike charges attract, and like charges repel.

What is the second law of electrostatics?

Electric charge on a conductor is concentrated along the sharpest curve of the surface.

What is the third law of electrostatics?

Electric charge distribution is uniform throughout or on the surface.

What is the fourth law of electrostatics?

Electrostatic force is directly proportional to the product of the charges and inversely proportional to the square of the distance between them.

What is electrodynamics?

The study of electric charges in motion.

What is electricity?

The flow of electrons through a conductor.

What is electric current measured in?

Amperes, or amps.

What is electric potential measured in?

Volts.

What is electric resistance measured in?

Ohms.

What is Ohm’s Law?

V = IR.

What does V stand for in Ohm’s Law?

Electric potential, measured in volts.

What does I stand for in Ohm’s Law?

Electric current, measured in amperes.

What does R stand for in Ohm’s Law?

Electric resistance, measured in ohms.

What happens to current if resistance increases and voltage stays the same?

Current decreases.

What happens to current if resistance decreases and voltage stays the same?

Current increases.

What is a circuit?

A closed path that allows electric current to flow.

What material is commonly used as a conductor in wires?

Copper.

What is the purpose of insulation around a wire?

It keeps electron flow inside the conductor and helps prevent shock.

What is direct current?

Electric current where electrons flow in one direction.

What is alternating current?

Electric current where electrons move back and forth.

What is the rule for total resistance in a series circuit?

Total resistance equals the sum of all individual resistances.

How does current behave in a series circuit?

Current is the same through every circuit element.

How does voltage behave in a series circuit?

Voltage is divided across the circuit elements.

What is the rule for voltage in a series circuit?

The sum of the voltage drops equals the total circuit voltage.

What is the rule for current in a parallel circuit?

Total current equals the sum of the currents in each branch.

How does voltage behave in a parallel circuit?

Voltage is the same across each branch.

How is total resistance found in a parallel circuit?

Total resistance is the inverse of the sum of the reciprocals of each resistance.

How many paths does current have in a series circuit?

One path.

How many paths does current have in a parallel circuit?

More than one path.

What happens to total resistance when more branches are added in parallel?

Total resistance decreases.

What creates a magnetic field?

Any charged particle in motion.

What direction is the magnetic field around a moving electron?

Perpendicular to the motion of the electron.

What is magnetism?

A fundamental property of some forms of matter.

What is a lodestone?

A naturally magnetic stone made of magnetite.

What are the four magnetic states of matter?

Nonmagnetic, diamagnetic, paramagnetic, and ferromagnetic.

What does nonmagnetic mean?

Unaffected by a magnetic field.

What does diamagnetic mean?

Weakly repelled by both magnetic poles.

What does paramagnetic mean?

Weakly attracted to both magnetic poles.

What does ferromagnetic mean?

A material that can be strongly magnetized.

What does a transformer do?

It changes electric potential and current to a higher or lower intensity.

What type of current does a transformer require?

Alternating current.

What is Faraday’s Law?

An electric current is induced in a circuit when part of the circuit is in a changing magnetic field.

What must be present for electromagnetic induction to occur?

Relative motion between the conductor and the magnetic field.

What factors affect the magnitude of induced current?

Magnetic field strength, speed of motion, angle of the conductor, and number of wire turns.

What did Oersted discover?

A current in a conductor creates a magnetic field around it.

What does the right-hand rule help determine?

The direction of the magnetic field or polarity.

What is an electromagnet?

A magnet created by electric current flowing through a coil.

How does a ferromagnetic core affect an electromagnet?

It strengthens the magnetic field.

What does an AC generator do?

Converts mechanical energy into electrical energy.

How does an AC generator work?

A coil rotates in a magnetic field, causing electrons to flow.

What does an electric motor do?

Converts electrical energy into mechanical energy.

How does an AC motor work?

Alternating current changes the poles of the coil, causing it to turn.

What does a DC motor use to keep the coil turning?

A split commutator ring.

What is the x-ray tube made up of?

External components and internal components.

What is the purpose of the ceiling support system?

It allows the x-ray tube to move longitudinally and transversely.

What is a floor-to-ceiling support system?

A single column with rollers that allows the tube to move up and down.

What is the protective housing made of?

Aluminum with lead lining.

What is the purpose of the protective housing?

It helps cooling, provides electrical insulation, and limits leakage radiation.

What does isotropically mean?

X-rays are emitted equally in all directions.

What are useful x-rays?

The x-rays emitted through the tube window.

What is the glass envelope?

The part of the tube that contains a vacuum and supports the internal components.

Why does the glass envelope contain a vacuum?

So electrons do not collide with gas atoms.

What is the tube window?

A thinner section of the glass envelope that allows x-rays to escape.

What side of the x-ray tube is the cathode?

The negative side.

What are the two main parts of the cathode?

The filament and focusing cup.

What is the filament made of?

Tungsten with a small amount of thorium.

What is the job of the filament?

It releases electrons when heated.

What is the job of the focusing cup?

It helps direct electrons toward the anode.

What side of the x-ray tube is the anode?

The positive side.

What does the anode do?

It conducts electricity, radiates heat, and contains the target.

What are the two types of anodes?

Stationary and rotating.

Where are stationary anodes commonly used?

Dental and some portal imaging systems.

Why are rotating anodes used?

They produce high-intensity x-ray beams in a short time and help dissipate heat.

What materials can be found in the anode?

Tungsten-rhenium alloy, copper, molybdenum, and graphite.

Why must the anode be a good thermal dissipater?

Because more than 99% of electron energy becomes heat.

What is the target?

The area of the anode struck by electrons from the cathode.

Why is tungsten-rhenium often used for the target?

It can withstand high-speed rotation and repeated heating and cooling.

What is the induction motor used for in the x-ray tube?

It rotates the anode.

What are the two main parts of the induction motor?

The stator and rotor.

Where is the stator located?

Outside the glass enclosure.

Where is the rotor located?

Inside the glass enclosure.

What does the rotor do?

It rotates the anode.

Why is heat a major issue in the x-ray tube?

Most of the electron energy becomes heat instead of x-rays.

Who primarily affects the life of the x-ray tube?

The technologist.

How can the technologist help protect the x-ray tube?

By allowing the anode to cool between high-temperature exposures.

What are the three ways heat can transfer?

Radiation, conduction, and convection.

What is the anode heel effect?

A variation in x-ray beam intensity caused by the angle of the anode target.

Why is understanding electricity important for radiographers?

X-ray production depends on voltage, current, resistance, and electromagnetic principles.

How does mA relate to current?

mA controls the amount of electron flow in the x-ray tube.

How does kVp relate to voltage?

kVp controls the electrical force pushing electrons from cathode to anode.

What happens when kVp increases?

Electrons gain more energy and the x-ray beam becomes more penetrating.

What happens when mA increases?

More electrons are available, producing more x-ray photons.

Why is the cathode negative and the anode positive?

Electrons are negatively charged and are attracted from the cathode to the positive anode.

Why does the anode need to handle heat well?

Because electron interactions at the target produce mostly heat.

What part of the tube allows x-rays to leave the tube?

The tube window.

What part restricts leakage radiation?

The protective housing.

What part helps focus electrons toward the target?

The focusing cup.

What part is struck by electrons to produce x-rays?

The target.

What part rotates the anode?

The rotor.

What part creates the magnetic field that turns the rotor?

The stator.