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Rad Physics (Radt 134) > Unit 4 Chapter 4 Electricity, Magnetism and Electromagnetism > Flashcards

Unit 4 Chapter 4 Electricity, Magnetism and Electromagnetism Flashcards

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1
Q

The science of stationary electric charges

A

electrostatics (static electricity)

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2
Q

the science of electric charges in motion

A

electrodynamics

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3
Q

the xray imaging system is made to do what

A

convert electric energy into electromagnetic energy

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4
Q

means of transferring electric potential energy from one position to another as in a transformer

A

electromagnetic induction

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5
Q

electric energy is supplied to the imaging system as a well controlled……

A

electric current

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6
Q

in the xray tube, some of the energy is converted to electromagnetic energy, while most is converted to …..

A

heat. 1% converted into xrays, 99% to heat

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7
Q

electric charges come in what kind of units

A

discrete units that are positive or negative

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8
Q

apart or detached from others; separate; distinct

A

discrete

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9
Q

most discussions of electric charge deal with?

A

negative electric charges associated with electrons

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10
Q

why are protons not as free to travel as electrons are

A

because they are bound so tightly in the nucleus

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11
Q

what kind of charge to electrons have?

A

one unit of negative charge

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12
Q

what kind of charge to protons have?

A

one unit of positive charge

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13
Q

protons and electrons have opposite signs(charges) but the same what?

A

magnitude

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14
Q

when an object has too many or too few electrons what does that mean

A

electrification

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15
Q

how do you CREATE electrification

A

by contact, friction or induction

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16
Q

some atoms have outer shell electrons that are loosely bound and can……

A

be removed easily

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17
Q

what happens when loosely bound electrons are removed

A

causes the object they were removed from to become electrified and produces static electricity

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18
Q

rubbing your feet on the carpet causes a buildup of electrons causing you to ……

A

become electrified

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19
Q

why does your hair stand up when you rub a balloon on your head?

A

the negatively charged particles are repulsed from each other

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20
Q

after creating static with a balloon on your hair, why wont it lay back down nicely

A

because the negative charged particles are trying to get away from each other

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21
Q

the earth is always available to accept excess electric charges…what is it called then

A

an electric ground

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22
Q

during a thunderstorm, electrons can be moved….

A

from cloud to cloud

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23
Q

how do clouds return to their normal state

A

lightining

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24
Q

lightning can occur between….

A

clouds of differing charges and between the clouds and the earth

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25
Q

coulomb (unit of electric charge)

A

1C=6.3 x 10^18

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26
Q

the electrostatic force is directly proportional to the product of the electrostatic charges and inversely proportional to the square of the distance

A

coulomb’s law

F=k QaQb/d^2

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27
Q

how is electric charge distribution?

A

uniform throughout or on the surface

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28
Q

electric charge of a conductor is concentrated

A

along the sharpest curvature of the surface

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29
Q

associated with an electric charge

A

electric field

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30
Q

what way does the field of a positively charged object point

A

outward

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31
Q

what way does the field of a negatively charged object point

A

inward

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32
Q

do uncharged particles have an electric field

A

no

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33
Q

how will the magnetic field of UNLIKE charges react to each other

A

the magnetic filed will pull them towards one another, the negative pulling inward and the positive pushing outward

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34
Q

how will the magnetic fields of LIKE charges react

A

they will cause objects to be physically repulsed from one another

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35
Q

electrostatic force is directly _______ to the product of electrostatic charges

A

proportional

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36
Q

the more charges that are present, the ______ the force will be

A

stronger

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37
Q

electrostatic force is _______proportional to the square of the distance between them

A

inversely

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38
Q

as distance increases, electrostatic force

A

decreases

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39
Q

how are electric charges distributed on the surface of copper wire

A

evenly

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40
Q

on a cattle prod, where will the charges be concentrated?

A

at the surface (it is a conductor and the tip is the curvature)

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41
Q

Think what when it comes to electric potential?

A

voltage

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42
Q

the measure of work required by and electric field to move electric charges

A

electric potential

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43
Q

the unit of electric potential

A

volt, also called voltage

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44
Q

electric charges have__________

A

Potential energy

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45
Q

electric charges can do work, when ______charges are close to each other, they can do work when they _____apart

A

like; fly

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46
Q

higher voltage means

A

a greater ability to do work

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47
Q

electric current is always opposite of ________

A

electron flow

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48
Q

what is it called when electric potential is applied to objects such as copper wire, then electrons move along the wire?

A

electric current, or electricity

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49
Q

any substance through which electrons flow easily

A

conductor(copper, aluminum)

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50
Q

any material that does not allow electron flow

A

insulator(Rubber, glass)

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51
Q

a material that under some conditions behaves as an insulator and in other conditions behaves as a conductor

A

semiconductor

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52
Q

the property of some materials to exhibit no resistance below a critical temperature

A

superconductivity

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53
Q

electrons flow alternately in one direction and then the other

A

ac current (alternating current)

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54
Q

electrons flow in one direction only

A

dc(direct current)

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55
Q

what kind of circuit has all circuit elements connected in a straight line along the same conductor

A

series circuit

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56
Q

what kind of circuit contains elements that are connected at their ends rather than lying in a line along a conductor

A

parallel circuit

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57
Q

formula for power

A

P=IV

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58
Q

path of electron flow from the generating source through the various components and back again

A

electric circuit

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59
Q

unit for current

A

Ampere (A)

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60
Q

unit for resistance

A

Ohms

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61
Q

the flow of electrons and measured in amperes

A

current

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62
Q

one ampere is equal to an electric charge of?

A

1C (coulomb) per second

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63
Q

electric potential is measured?

A

volts

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64
Q

changing the size of the wire electrons may flow through _____ the resistance of the circuit

A

varies

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65
Q

as resistance______, current_______

A

increases; decreases

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66
Q

the voltage across the total circuit or any portion of the circuit is equal to the ___

A

current times the resistance

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67
Q

V=IR and????

A

R=V/I and I=V/R

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68
Q

what is the current of an electric voltage that flows 10 amps and has a resistance of 0.5 ohms?

A

5 volts

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69
Q

two basic types of circuits are?

A

parallel and series

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70
Q

in a series circuit, all circuit elements are connected in a ___ along the same conductor

A

line

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71
Q

in a parallel circuit, elements are connected at their ___rather than lying in a line along a conductor

A

ends

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72
Q

the total resistance is equal to the ___of all resistances

A

sum

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73
Q

the current through each circuit element is the same and equal to the

A

total circuit current

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74
Q

the sum of the ____ across each circuit element is equal to the total circuit voltage

A

voltage

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75
Q

the total resistance is the __ of the sum of the reciprocals of each individual resistance

A

inverse

76
Q

the sum of the current through each circuit element is equal to the __circuit current

A

total

77
Q

the voltage across each circuit element is the same and is ___ to the circuit voltage

A

equal

78
Q

Christmas lights can be wired in a

A

series or parallel circuit

79
Q

when Christmas lights are wired in a series, one light going out——-

A

causes the entire circuit to go out. the circuit has been broken

80
Q

when Christmas lights are wired in a parallel, one light going out

A

does not cause the circuit to break, and the string will continue glowing aside from the bad bulb

81
Q

electrons which flow only in one direction

A

direct current

82
Q

electrons which oscillate back and forth

A

alternating current (example electric plug)

83
Q

in a direct current (dc) what does the horizontal axis (x) and vertical axis (Y) represents

A

x=time

Y=voltage

84
Q

DC is represented as a straight line since the ___ are always flowing in the same direction

A

electrons

85
Q

ac current can be represented by what?

A

a sine wave

86
Q

at 0, how are the electrons?

A

at rest

87
Q

at 1, electrons have reached max flow, the voltage is at its___

A

highest point

88
Q

at 2, electrons go to zero voltage again momentarily and ____ directions

A

shift

89
Q

at 3, the electrons have reached _____potential in the opposite direction

A

maximum

90
Q

how often does the oscillation happen with AC

A

1/60 of a second. every 1/60 of a second it changes direction. 60 cycles every second

91
Q

AC is how many Hz current?

A

60Hz

92
Q

how is electric power measured?

A

in Watts (W)

93
Q

our common household items operate between 500-1500W, the x ray imaging system requires how much?

A

20,000-150,000 (W)

94
Q

one watt is equal to what?

A

1 amp flowing through an electric potential of volt

95
Q

around 1000 BC, shepherds and dairy farmers in Magnesia would use a ____to find water

A

lodestone

96
Q

when suspended from a string the lodestone would rotate back and forth when it came to rest it would point towards ____

A

water

97
Q

what was the lodestone really pointing too?

A

magnetic north

98
Q

any charged particle in motion creates……

A

a magnetic field

99
Q

can you sense magnetism?

A

no, it is difficult to detect and measure

100
Q

the magnetic field of a charged particle in motion is ….

A

perpendicular to the motion of that particle

101
Q

the magnetic field is neutralized how?

A

in magnetic pairs

102
Q

atoms with an odd number of electrons in any shell have a very small…

A

electric field

103
Q

spinning electric charges induce a magnetic field along the ……of the spin

A

axis

104
Q

lines of a magnetic field do not start or end such as with an electric field. this continuous field is called ______

A

bipolar or dipolar

105
Q

current that flows in an infinitesimally(minute) small loop

A

magnetic dipole

106
Q

an accumulation of many atomic magnets with their dipoles aligned

A

magnetic domain

107
Q

how are magnetic domains distributed normally?

A

randomly

108
Q

when exposed to an external magnetic field, the domains can ____

A

align

109
Q

if all the magnetic _____ in an object are aligned, it acts like a ___

A

domains; magnet

110
Q

how are magnets classified?

A

according to the origin of the magnetic property

111
Q

natural magnets

A

the earth, lodestones

112
Q

artificially induced permanent magnets

A

iron bar magnets, compass

113
Q

wire wrapped around an iron core

A

electromagnets

114
Q

a magnetic field is created when….

A

a current is conducted through the electric wire

115
Q

the intensity of the magnetic field is ________to the current

A

proportional

116
Q

the higher the current, the greater the ____ of the magnetic field

A

intensity

117
Q

materials which are weakly repelled by either magnetic pole

A

diamagnetic

118
Q

materials which are strongly attracted by a magnet and can be permanently magnetized

A

ferromagnetic

119
Q

types of ferromagnets

A

iron,cobalt and nickel

120
Q

these materials are slightly attracted to a magnet

A

paramagnetic

121
Q

material which are unaffected by a magnetic field, wood, glass

A

nonmagnetic

122
Q

the imaginary lines of a magnetic field leave the north pole and ____return to the ___pole

A

leave; south

123
Q

the SI unit for magnetic field strength

A

tesla (T)

124
Q

magnets on our fridge are about how many teslas?

A

100mT

125
Q

an MRI operates at how many teslas?

A

3T

126
Q

what was a precursor to the modern battery?

A

a voltaic pile

127
Q

Italian physicist in the 1700s that used zinc and copper plates to create an electric current

A

Alessandro Volta

128
Q

who discovered a link between electric and magnetic forces?

A

Hans Oersted in 1820

129
Q

an electric current is induced in a circuit if some part of that circuit is in a changing magnetic field

A

electromagnetic induction

130
Q

Faraday’s Laws( 4 of them)

A

the magnitude of the induced current depends on four factors:

  1. the strength of the magnetic field
  2. the velocity of the magnetic field as it moves past the conductor
  3. the angle of the magnetic field to the conductor
  4. the number of turns in the conductor
131
Q

2 basic parts of an induction motor

A

stators and a rotor

132
Q

what are stators?

A

stationary electromagnets

133
Q

The smallest unit of electrical charge is the _____.

A

electron.

134
Q

Like charges _____ and unlike charges _____.

A

Like charges repel and unlike charges attract.

135
Q

Electrostatic force is _____ proportional to the distance between charges, and _____ proportional to the product of the charges.

A

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

136
Q

On the surface of an electrified object, the charges concentrate on the _____.

A

sharpest curvature.

137
Q

A _____ is a source of direct current.

A

battery

138
Q

What is the unit of electric potential?

A

volt

139
Q

An electric potential applied to a conductor produces _____.

A

When an electric potential is applied to a conductor, both an electric current and a magnetic field are produced.

140
Q

An alternating (AC) current is represented by a _____ line.

A

sinusoidal line

141
Q

A _____ uses direct current.

A

A flashlight is battery operated, and batteries use direct current.

142
Q

Alternating current is produced by a _____.

A

generator.

143
Q

What is Ohm’s law?

A

Ohm’s law is I = V/R

144
Q

A charged particle in motion creates a(n) _____.

A

magnetic field.

145
Q

Electrical power is measured in _____.

A

watts.

146
Q

Rubber and glass are _____.

A

insulators because they are nonconductors.

147
Q

When a group of dipoles are aligned, they create _____.

A

a magnetic domain

148
Q

In the United States, alternating current goes through a complete cycle every _____ second.

A

1/60 second.

149
Q

What is the SI unit of magnetic field strength?

A

tesla or gauss.

150
Q

The force between magnetic poles is proportional to the _____ of the magnetic pole strengths, divided by the _____ of the distance between them.

A

The force between magnetic poles is proportional to the PRODUCT of the magnetic pole strengths, divided by the SQUARE of the distance between them.

151
Q

What type of material can be made magnetic when placed in an external magnetic field?

A

Ferromagnetic material

152
Q

Like magnetic poles _____ and unlike magnetic poles _____.

A

Like magnetic poles REPEL and unlike magnetic poles ATTRACT.

153
Q

Water is a _____ material

A

diamagnetic

154
Q

The magnetic intensity of an electromagnet is greatly increased by the addition of a(n) _____ core

A

iron

155
Q

A magnetic field is produced by

A

electric charges in motion

156
Q

A generator is a device that converts

A

mechanical energy to electrical energy.

157
Q

A motor is a device that converts

A

electrical energy into mechanical energy.

158
Q

A transformer with more secondary windings than primary windings

A

has a greater secondary voltage

159
Q

The turns ratio of a transformer is determined by the

A

number of windings

160
Q

All of the following are true of induction motors EXCEPT:

  1. They use multiphase current and can turn at varying rpm.
  2. Motor power can be regulated by the characteristics of the electromagnets that make up the stator.
  3. Their design is inherently weak with regard to power.
  4. They are used to spin the x-ray tube anode disk.
A

3.Their design is inherently weak with regard to power.

161
Q

The electric field of a positive electric charge points____________, the electric field of a negative electric charge points___________

A

OUTWARD;INWARD

162
Q

Increasing the product of electric charges will ___________electrostatic force

A

increase

163
Q

Increasing the distance between electric charges will_____________elestrostatic force.

A

decrease

164
Q

Electric current is always ___________ electron flow.

A

opposite

165
Q

Electricity flows easily through ___________, but does not flow through_________.

A

copper or wood; a conductor or an insulator

166
Q

What material behaves sometimes as a conductor and sometimes as an insulator?

A

semiconductor

167
Q

What type pf material is greatlly influenced by temperature?

A

superconductors

168
Q

One ampere is equal to:

A

1 Coulomb per second

169
Q

Which of the following is NOT a variation of Ohm’s Law?
1. V=IR

  1. R=V/I
  2. V=IRR
  3. I=V/R
A

V=IRR

170
Q

A series circuit contains 3 resistors of 5 Ohms, 10 Ohms and 15 Ohms. what is the toal resistance of the circuit?

A

30 ohms

171
Q

What type of current is wired to our homes and businesses?

A

AC

172
Q

What type of current must an X ray imaging system use

A

DC

173
Q

Which of the following is not a variation of the formula for electric power?

  1. V=IR
  2. P=IV
  3. P=IIR
  4. P=I2R
A

V=IR

174
Q

Magnetic field lines are ____________to the plane of travel of a charge.

A

perpendicular

175
Q

Adding loops to a solenoid will

A

Increase the intensity of the magnetic field

176
Q

Magnetically, an electromagnet acts ________________ as a bar magnet.

A

the same

177
Q

In an electromagnet, current effects the magnetic field:

A

Directly

178
Q

In an induction motor, _______________is responsible for causing the rotation of the rotor.

A

stators and electromagnets

179
Q

The current of a series circuit is measured in three places with results of 10A, 10A and 10A. What is the total current of the circuit?

A

10A

180
Q

The voltage of a series circuit is measured in 3 different places with results of 10V, 10V and 10V. What is the total voltage of the circuit?

A

30V

181
Q

The current of a parallel circuit is measured in three places with results of 10A, 10A and 10A. What is the total current of the circuit?

A

30A

182
Q

The voltage of a parallel circuit is measured in 3 different places with results of 10V, 10V and 10V. What is the total voltage of the circuit?

A

10V

183
Q

If a transformer has 10 turns on the primary coil and 100 turns on the secondary coil, what is the turns ratio?

A

10:1

184
Q

A transformer has 1000 turns in the primary coil and 10 turns in the secondary coil. It is supplied with 50 a and 1000 V, what is the output current and voltage?

A

10 volts secondary and 5,000a

185
Q

A parallel circuit contains 3 resistors that are each 10 Ohms. What is the total resistance of the circuit?

A

.1+.1+.1=.3 reciprocal of .3 is 3.33<—–answer

Rad Physics (Radt 134) (6 decks)

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