Chapter 4 p2 - Conductors, Electronic Devices

A/C:

• flows in both directions

• 60 cycles per second

• hertz defined as one cycle per second

• electricity alternates at frequency of 60 hertz (cycles) per second in US

D/C:

• flows in one direction

• battery flow from negative to positive electrodes

DC – Electrons flowing in only one direction. Represented by:

• a straight line

• can also be pulsed, but doesn’t lose current

Resistance is measured in ohms, named after the physicist:

• George Simon Ohm

• discovered the Inverse relationship between current and resistance

• current increases, resistance decreases

Ohm is the:

electrical resistance equal to the resistance between two points along a conductor that produces a current of 1 ampere when a potential difference of 1 volt is applied

Ohm’s law is the:

potential difference (voltage) across the total circuit or any part of that circuit, is equal to the current (amperes), multiplied by the resistance

V = I*R

V = volts, I = current (amps) R = resistance

An alternating current (A/C) is described as:

• electrons flowing alternately in opposite directions

• represented by a sinusoidal line produced by a generator

The amount of resistance of current in a conductor depends on four things:

1. material

2. length

3. cross-sectional area

4. temperature

Resistance is a useful and important part of the process of:

x-ray production

semiconductors:

materials that will conduct electricity but not as well as conductors and that will insulate but not as well as insulators

conductors:

materials with an abundance of free electrons that allow a relatively free flow of electricity

Examples of electrical conductors:

water, gold, copper, steel

Examples of electric insulators:

rubber, glass, oil, diamond, dry wood

Semi-conductors devices:

• op-amp

• resistors

• capacitator

• diodes

• transistors

• ICs

A closed (complete) pathway composed of wires and circuit elements through which electricity may flow:

an electric cicuit

In an electric circuit, closed means _____, and open means _____.

complete; broken

Series Circuits are calculating for:

the current (amps)

Electronic devices in radiography:

• battery

• capacitor

• diode

• protective devices (fuses and circuit breakers)

• resistor or rheostat

• switch

• transformer

Battery:

• produces electrons through a chemical reaction

• stores an electric charge long term

• provides an electric potential.

Capacitor:

• temporarily stores an electric charge.

• cannot produce more electrons

• stores charge temporarily

Diode:

a “one-way valve” device; allows electrons to flow in only one direction

Fuses (protective devices):

• emergency devices that break or open the circuit if there is a sudden surge of electricity to the circuit or device.

• fuse - wire in glass, melts if current rises excessively

Circuit Breaker- internal switch tripped open:

Resistor:

inhibits the flow of electrons, thereby precisely regulating the flow of electricity through that part of the circuit where it is placed

Rheostat:

is simply an adjustable or variable form of resistor

Switch:

a device that opens a circuit (breaks the pathway)

Transformer:

a device that can increase or decrease voltage by a predetermined amount

What happens to the positively charged objects when grounded?

they take on electrons from the earth

What happens to the negative charged objects when grounded?

they give up electrons to the earth until neutral