S6 electricity - 3. resistivity and superconductivity

Question 1

what are the three things that determine resistance?

Answer 1

+ Length
+ Area
+ resistivity

Question 2

how does the Length of a wire affect resistance?

Answer 2

The length of the wire is directly proportional to resistance

The longer the wire, the more difficult it is to make a current flow, resulting in higher resistance.

Question 3

how does the cross-sectional area of a wire affect resistance?

Answer 3

the cross-sectional area of a wire is inversely proportional to resistance

The wider the wire, the easier it is for electrons to pass through it

Question 4

how does the resistivity of a wire affect resistance

Answer 4

Resistivity depends on the material. The structure may make it easy or difficult for charge to flow.

Environmental factors such as temperature and light intensity can affect resistivity.

Question 5

define resistivity

Answer 5

The resistivity of a material is defined as the resistance of a 1m length wire with a 1m² cross-sectional area.

resistivity is measured in ohm-meters (Ωm)

Question 6

state the formula for resistivity

Answer 6

ρ = RA / L

R = resistance
A = area
L = length

Question 7

state a property of a superconductor

Answer 7

Superconductors have zero resistivity

Question 8

what is the critical temperature for most metals

Answer 8

most normal conductors have critical temperatures below 10 kelvin (-263°C)

Question 9

state a few uses of superconductors

Answer 9

+ power cables that transmit electricity without any loss of power

+ really strong electromagnets that don’t need a constant power source (medical applications and maglev trains)

+ electronic circuits that work really fast, because there’s no resistance to slow them down