Functional Properties And Environmental Interactions

Question 1

Formula for capacitance

Answer 1

C = Q/V or Q = CV

Where Q is the charge on the capacitor, V is the voltage across it, and C is the capacitance (duh)

Question 2

What are the units of capacitance?

Answer 2

Farads (F)

Which represent Coulombs per Volt (Q/V)

Question 3

What is capacitance?

Answer 3

The ability of a capacitor to store charge

Question 4

What are some functional and structural properties?

Answer 4

Functional: optical, electrical, magnetic, thermal

Structural: malleability, hardness, toughness, strength, corrosion resistance

Question 5

Ductility vs malleability

Answer 5

Ductility is the degree to which a material stretches when put under tensile strengths. This affects the material’s ability to be pulled into a wire

Malleability is a material’s ability to deform under pressure/compressive stress. This affects its ability to be squashed and flattened

Question 6

Important engineering and functional properties of ceramics

Answer 6

Engineering: refractory (heat resistant), hard, brittle, enreactive, strong

Functional: you can look these up for fun
Magnetic, electrical conduction and insulation, dielectric behaviour, low thermal conductivity, tuneable optical absorption and emission, environmentally dependent surface properties

Question 7

Important engineering and functional properties of polymers d

Answer 7

Engineering: low density, plastic or brittle depending on temperature, low elastic modulus (compliant)

Functional: magnetic, electrical conductivity? Low thermal conductivity, light emission

Question 8

Important engineering and functional properties of metals

Answer 8

Ductile and malleable, melt at moderate temperatures, reactive easily oxidised

Magnetic behaviour
Electrical and thermal conduction

Question 9

Perfect conductor and insulator

Answer 9

A perfect conductor is a hypothetical material in which the charge distribution responds instantaneously to stimuli

A perfect insulator is a hypothetical material in which any charge distribution will persist for an infinite length of time

Question 10

What is the amount of work done (dW) when moving an electric charge Q in an electric field E?

Answer 10

dW = Fds = -qEds

Question 11

Electric dipole moment

Answer 11

p = qa

P is the electric dipole moment, q is the magnitude of charge of each charge, a is the distance between them

Question 12

Current density J

Answer 12

J = I/A

J = sigmaE

Sigma is the conductivity of the material

Sigma =1/p

p is rho, the résistivité of the material

Question 13

Resistance R

Answer 13

R = l/(A*p)

p is rho the resistivity

Question 14

Magnetic force due to two parallel wires

Answer 14

dF2 = (u0I1I2ds1ds2)/(4pir^2)

u0 = magnetic constant/permeability of a vacuum = 4pi*10^-7 NA^2

Question 15

Magnetic flux due to a wire

Answer 15

dB1 = (u0I1ds1)/(4pir^2)

Basically remove ds2 and I2

dF2 = ds2I2dB1

Question 16

Lorentz force

Answer 16

F = Felectro +Fmagnetic =
qE + qvB

Force parallel to E and perpendicular to both v and B

Question 17

Which way on the voltage gradient do positive charges move

Answer 17

Positive charges move down the electric potential (voltage) gradient

Question 18

Electric constant (permittivity of vacuum)

Answer 18

Epsilon subscript 0 but it doesn’t look like he squiggly E like strain, it looks like the euro sign (Chegg)

8.85*10^-12 C^2 N^-1 m^-2

Question 19

Magnetic constant (permeability of free space/vacuum)

Answer 19

uo (mu subscript 0) is 4pi10^-7 NA^2

Question 20

Macroscopic polarisation of a material P

Answer 20

P = np

n is the number density of dipoles in the material

p is the polarisation of the individual dipoles (dipoles align with the electric field so p goes from the negative to the positive side of the dipole)

P and p are vectors

Question 21

What are the three types of polarisation?

Answer 21

Induced dipoles (in the atoms)

Permanent dipoles (e.g. H2O molecule)

Ion displacement

Question 22

Coulomb’s law in a dielectric

Answer 22

Replace the permittivity of free space (€0)with the permittivity of the dielectric (€)

Check chegg

Question 23

Linear, areakej, and volumetric expansion

Answer 23

deltaL = loalphadeltaT
Or
deltaL/lo = alpha*deltaT

Where alpha (subscript lowercase L) is the linear coefficient of expansion

deltaA/Ao = 2*alpha*deltaT
deltaV/Vo = 3*alpha*deltaT

Question 24

Flux

Answer 24

What does it mean and google the word for “of area”. Linear, of area, volumetric

Question 25

Motile

Answer 25

Vs mobile