Lecture 4

Question 1

Coulombs Law

Answer 1

F= k (q1q2)/r^2

k = 9x10^9 N*m^2/C^2

Question 2

Charge of 1 e

Answer 2

1.6 x 10^-19

Question 3

Field

Answer 3

condition is space that creates a force on a charge

any force must be in contact except for gravity, electricity, and magnetism

Question 4

Lines of force

Answer 4

represents field, point in direction of field (positive to negative)

distance between lines indicates strength of field (closer together means stronger field)

Question 5

Electric field

Answer 5

E, electrostatic force per unit charge

E= k (q1/r^2)F

Question 6

Force in electric field

Answer 6

Force on a charge q in electric field

F= qE

Question 7

Potential energy of a charge

Answer 7

U= qEd

d- displacement

Question 8

Voltage

Answer 8

potential for work by an electric field in moving any charge from one point to another

V=Ed

Question 9

Voltage due to point charge

Answer 9

V= k (q1/r)

Question 10

equipotential lines

Answer 10

movement perpendicular results in no change in potential

points are at same voltage

Question 11

electric dipole

Answer 11

two opposite charges with equal magnitude

p=qd

points in direction opposite to the electric field

Question 12

conductors

Answer 12

electrons flow freely

Question 13

resistors

Answer 13

poor conductors, hold electrons tightly in place

Question 14

current

Answer 14

moving charge, in amps or C/s

direction of movement of positive charge

Question 15

What affects resistance

Answer 15

Increasing length of wire increases distance

increasing area (increasing radius) decreases resistance

Question 16

Resistance

Answer 16

measure of an object of certain size/shape to resist the flow of charge

in Ohms

R= (resistivity)(L/A)

length/area

Question 17

How does resistance vary with temperature

Answer 17

R= R0 [1+ alpha (T-t0)]

increase in temperature leads to increase in resistance

Question 18

Ohms Law

Answer 18

V=IR

V= voltage/potential difference

Question 19

capacitor

Answer 19

temporarily stores energy in a circuit

stores energy in the form of separated charge

separation creates an electric field

Question 20

parallel plate capacitor

Answer 20

two places of conductive material separated by a small distance

one holds positive, other holds same amount of charge but negative

electric field is constant everywhere between plates

Question 21

Electric field of parallel capacitor

Answer 21

E= (1/k)(Q/AE0)

k= dielectric
q= charge on plate

Question 22

Dielectric k

Answer 22

k= 1/(4piE0)

substance between the plates of a capacitor

acts like a insulator and resists formation of electric field

Question 23

capacitance

Answer 23

ability to store charge per unit of voltage

high capacitance can store a lot of charge art low voltage

C=Q/v

Question 24

Charge in parallel plate

Answer 24

charge is proportional to area, charge is on surface so thickness does not matter

father separated means greater voltage and lower capacitance

Question 25

Parallel plate capacitance equation

Answer 25

C= k (AE0/d) C increases as area increases and as distance decreases

Question 26

Energy stored in a capacitor

Answer 26

U=1/2 QV Q=CV

Question 27

In series

Answer 27

any two components NOT separated by a node

Question 28

In parallel

Answer 28

Single components in alternate paths connecting the same nodes

Question 29

Resistors in series

Answer 29

Charge drops each time it passes and dissipates energy Reff= R1+R2 + R3... increasing length will increase R Total length= sum resistors

Question 30

Resistors in parallel

Answer 30

1/Reff= 1/R1 + 1/R2 ... area= sum of area, increasing area will decrease resistance voltage drop is the same, have lower resistances to pass through

Question 31

Capacitors in series

Answer 31

1/Ceff= 1/C1 + 1/C2.... increasing distance will decrease capacitance distance total= distance between first and last capacitor

Question 32

Capacitors in parallel

Answer 32

Ceff= C1 +C2... area= sum increasing area will increase capacitance (can spread out and have smaller repulsive)

Question 33

Ammeter

Answer 33

measures current flowing through a circuit uses series of circuit R=0 to maximize current

Question 34

Voltmerer

Answer 34

measures potential difference between two points attached at two points on circuit in parallel does not draw current - infinite resistance

Question 35

multimeter

Answer 35

ammeter and voltmeter switch to determine

Question 36

magnetic field

Answer 36

measured in tesla, created by moving charges

Question 37

magnetic field lines

Answer 37

north to south

Question 38

magnets in field

Answer 38

force pulls south pole opposite direction of magnetic field lines, north in same direction as lines

Question 39

What does changing an electric field do

Answer 39

creates a magnetic field AND Changing a magnetic field creates an electric field

Question 40

Magnetic force

Answer 40

experienced by a charge moving through a magnetic field perpendicular to velocity and magnetic field F=qvBsin theta