topics 7-9

Question 1

whats electrostatic

Answer 1

the study of electric charges at rest

Question 2

whats voltage

Answer 2

electric potential differenceo

Question 3

voltage units

Answer 3

J / C (potential energy / unit charge)

Question 4

whats radiation

Answer 4

the transfer of heat by emission of infared radiation

Question 5

whats conduction

Answer 5

the transfer of energy

Question 6

whats convection

Answer 6

transfer of heat by movement of heated substance

Question 7

whats coulombs law

Answer 7

F = k (Q1.Q2/d^2)

Q1 , Q2 are charges
K = coloumb’s constant

Question 8

whats mAs equivalent

Answer 8

mC

Question 9

whats electrodynamics

Answer 9

the study of electric charges in motion

Question 10

whats current

Answer 10

the rate at which positive charges moves in a wire

Question 11

whats current equation

Answer 11

Q/t
Q = total charge

Question 12

what does a transformer do

Answer 12

transforms electric potential and current into a higher or lower intensity (changes the magnitude of a sinusoidal voltage)

Question 13

whats ohms law

Answer 13

V = IR
voltage = current x resistance

Question 14

what are the units in ohms law

Answer 14

V = volt
I = amperes
R = ohms

Question 15

whats a voltage drop

Answer 15

the decrease in electric potential (voltage) as current flows through and converts to electrical energy

Question 16

whats the voltage drop around an electrical circuit

Answer 16

0

Question 17

whats the total resistance in a parallel circuit

Answer 17

1/Rt = 1/sum of resistance (add the reciprocals of each and find the reciprocal of that)

Question 18

whats the total current in a parallel circuit

Answer 18

the sum of all currents

Question 19

whats the total current in a series circuit

Answer 19

the current is identical
I1 = I2 = I3 etc

Question 20

whats the total resistance in a series circuit

Answer 20

the sum of all individual resistances

Question 21

whats the total voltage in a series circuit

Answer 21

Vt = V1 + V2
so V = IR
therefore V = (I(R1 +R2)

Question 22

whats the total voltage in a parallel circuit

Answer 22

voltage drop around any loop must be zero
therefore, VT = V1 = V2

Question 23

what power equation in direct circuit

Answer 23

P = I.V
P = I^2.R
P = V^2/R

Question 24

whats power equation in AC

Answer 24

P = iv (rms)
P = i^2.R
P = v^2/R

Question 25

how is an electrical current and magnetism related

Answer 25

moving electric charges produces a magnetic field

Question 26

whats a bar magnet

Answer 26

N atoms that carry a permanent magnetic moment (in parallel)

Question 27

whats diamagnetic

Answer 27

very weak (basically zero) interaction with external magnetic field (H)

Question 28

whats paramagnetic

Answer 28

weak interaction with external magnetic field (H)

Question 29

whats ferromagnetic

Answer 29

strong interaction with external magnetic field (H)

Question 30

whats a solenoid

Answer 30

a coil of wire that produces strong magnetic fields

Question 31

when is a solenoid's magnetic field strongest

Answer 31

in the middle of the coils, because the magnetic fields line up parallel acting like bar magnets

Question 32

magnetic field strength (H) units

Answer 32

A / m

Question 33

magnetic field strength (H) equation

Answer 33

(Number of turns in solenoid / length of solenoid) . current

Question 34

what's field of induction (B)

Answer 34

the total magnetic field that includes both magnetic fields from wire and any magnetisation (material related)

Question 35

field of induction (B) units

Answer 35

tesla (T) = N/A.m

Question 36

field of induction equation

Answer 36

magnetic permeability of a vaccum (mu 0) x relative permeability of the material placed in the field H (mu r) x H

Question 37

whats M in the field of induction equation

Answer 37

permeability material magnetisation ( the total magnetisation of an object from the tiny magnetic moments )

Question 38

whats the equation for permeability material magnetisation

Answer 38

chi . H chi = relative permeability - 1 (magnetic susceptibility)

Question 39

relatively permeability of non-magnetic

Answer 39

chi = 0 relative permeability = 1

Question 40

relatively permeability of diamagnetic

Answer 40

chi = -10^-3 relative permeability = 1 - 10^-3

Question 41

relative permeability of paramagnetic

Answer 41

chi >- 0 but really small = 1

Question 42

relative permeability of ferromagnetic

Answer 42

chi = greater than 0e

Question 43

the difference between straight wires and solenoids

Answer 43

straight wires produces magnetic fields that behave in circular loops solenoids produce parallel magnetic fields like bar magnet

Question 44

whats the H in straight wires

Answer 44

current / 2pi.r

Question 45

whats magnetic force

Answer 45

the force experience when a current-carrying wire (I) is placed in a uniform magnetic field (B)

Question 46

why does magnetic force occur

Answer 46

because the magnetic field around the wire interacts with the external field

Question 47

magnetic force equation

Answer 47

F = B.I (current). L(length of wire) . sin(theta) (angle between direction of flow and B)

Question 48

whats electromagnetic flux

Answer 48

how much magnetic field passes through an area

Question 49

what is the direction of a magnetic field through the wire of surface A

Answer 49

magnetic field lines are always perpendicular to the surface area

Question 50

electromagnetic flux equation

Answer 50

BAcos(theta)

Question 51

what is cos in electromagnetic flux when the wire is horizontal

Answer 51

flux is max when normal (the direction of flux) is parallel to B direction (assume constant magnetic field upwards direction) therefore cos = 1

Question 52

what is cos in electromagnetic flux when wire is rotated to 90 degrees

Answer 52

flux is min when normal is perpendicular to B direction flux is coming out of page

Question 53

how does voltage relate with change of flux

Answer 53

voltage is proportional to the rate of change of flux because the voltage acts to counter the current going through wire (therefore there's a negative)

Question 53

whats electromagnetic induction

Answer 53

when a current is induced in the wire loop when the magnetic flux changes

Question 54

how does transformer work

Answer 54

- primary wire changes current - this changes B field - induces a change in flux - induces current in second wire - second wire tries to resist and send out a current