* Physics Review (Unit 1)

In nature and associated with many familiar objects

Where do sine waves exist, and what are they associated with?

Velocity, Frequency, Wavelength

What three wave parameters are needed to describe electromagnetic energy?

Frequency

What refers to the number of wavelengths that pass a point of observation per second, the Rate of rise and fall?

Wavelength

What refers to the distance from one crest to another?

Wavelength and frequency are inversely proportional

What is the relationship between wavelength and frequency?

The speed of light (velocity)

Everything on the electromagnetic spectrum travels at what?

Amplitude

What refers to the distance from crest to zero or the height of the sine wave?

- 3 x 10^8 m/s

- 3 x 10^10 cm/s

- 186,000 miles/s

What are the measurements for the speed of light (velocity)?

- Velocity= frequency x wavelength

- v=fλ

- c=fλ

What is the speed of light (velocity) formula?

- Decreases

- Increases

- If energy (kvp) is increased, what happens to wavelength?

- If energy (kvp) is increased, what happens to frequency?

Radio waves ➜ Microwaves ➜ Infrared ➜ Visible light ➜ UV ➜ X-ray ➜ Gamma rad. ➜ Cosmic rad.

What is included in the electromagnetic spectrum from the longest wavelength to the shortest wavelength?

Radio waves (MRI), Visible light, X-ray (diagnostic),

Gamma rad. (nuc. med, rad. therapy, PET)

What regions of the electromagnetic spectrum are important to radiologic science?

Because it requires matter to bounce off of

Why is ultrasound not part of the electromagnetic spectrum?

- Quantity / Amperage

- Force / Potential Difference

- Opposition / Resistance

- Direction / AC or DC

What are the four common factors used to describe current flow?

Amperage (Amps or mAs)

What refers to the quantity or number of electrons flowing per second?

Potential Difference (voltage or electromotive force)

What is used to describe the force with which electrons travel or the strength of electron flow?

Places of abundance to places of deficiency

How do electrons flow?

Resistance (ohms)

What refers to the amount of opposition to the current within a circuit?

- V=IR

- I=V/R

- R=V/I

What is Ohm's law?

- Current in amps

- EMF/PD in volts

- Resistance in ohms

- I =?

- V =?

- R =?

Alternating Current (AC)

What type of current has electrons that flow in both directions and continuously switch back and forth in a sinusoidal pattern?

Direct Current (DC)

What type of current has electrons that only flow in one direction?

AC generator and DC generator

What are the two types of generators?

AC Generator

What type of generator has slip rings and brushes that connect to an armature, allowing it to turn and maintain a connection with the circuit?

A negative pulse and a positive pulse (2 pulses)

One turn of an AC generator is what?

The alternating rotation of the armature

What causes electrons to constantly change direction in an AC generator?

DC Generator (DC Pulsating)

What type of generator exchanges slip rings for commutator rings that causes the current to flow in the same direction and can produce a pulsating current?

Commutator Rings

What refers to a single ring that is cut in half, with each half connected to the end of the armature?

Transformer

What is an electromagnetic device that changes AC from a low voltage to a high voltage or a high voltage to a low voltage without the use of moving parts?

Electromagnetic mutual induction

How does a transformer work?

Primary Coil (Input Side)

In a transformer, where does electricity enter?

Secondary Coil (Output Side)

In a transformer, where does electricity leave?

A magnetic field is produced

As electricity enters the primary coil of wire during electromagnetic mutual induction, what happens?

- 1/120 of a second

- The magnetic field is constantly realigning the N/S poles, creating a moving magnetic field

- During electromagnetic mutual induction, how often does the AC change?

- What does this cause?

Electricity is produced within the secondary coil

Because the secondary coil of wire is within a moving magnetic field, what happens?

Step-Up Transformer

If there are more turns in the secondary coil than the primary coil, what kind of transformer is this?

- Increase

- Decrease

- What happens to the voltage in a step-up transformer?

- What happens to the amperage in a step-up transformer?

Step-Down Transformer

If there are more turns in the primary coil than the secondary coil, what type of transformer is this?

- Decrease

- Increase

- What happens to the voltage in a step-down transformer?

- What happens to the amperage in a step-down transformer?

Autotransformer

What refers to a single winding of wire wrapped around a large iron core that has connections to select the amount of voltage needed?

Kilovoltage (kV)

What does an autotransformer control?