resistance and resistivity

Question 1

Why use gold in circuits

Answer 1

Excellent conductor

number density almost as high as copper

much less reactive so corrodes very little over time

used in high energy electrical applications

and fine wires that connect pins on computer chips to integrated circuit boards

Question 2

4 factors of resistance

Answer 2

Temperature

Material

length of wire

cross sectional area of the wire

Question 2

Is resistance or resistivity unique

Answer 2

resistivity of a material is unique

ie copper has a unique resitivity

Question 3

what does term resitivity mean

Answer 3

used to describe electrical property of material

Question 4

What happens to PD and RESISTANCE when length of wire doubles

and whats proportionality of resistance and length

Answer 4

PD doubles too x2, So resistance doubles

restiance proportional to length

Question 5

What is relationship between Resistance and length in terms of poroportionality

Answer 5

Resistance is directly proportional to length

Question 6

What happens if cross sectional area of wire increases

Answer 6

resistance decreases

Question 7

Whats proportionality relationship between resistance and cross sectional area

Answer 7

Resistance is inversly proportional to 1/A

R= 1/A

Question 8

What is the equation for restitivity and resistance and the name of the symbol for restitivity.

and significance of each letter in equation

Answer 8

R = PL/A

P= RA/L

p is rho symbol

R is resitance
A is area
L is length

Question 9

What is resitivity measured in

Answer 9

ohm metre

Question 10

what is the equation needed to calculate cross sectional area

Answer 10

pie r squared

Question 11

What happens to resitivity when temps increase

Answer 11

Resistivity increases

Question 12

How to do resitivity experiment

Answer 12

1. Make a circuit with terminal, ammeter,voltmeter
2. Use a piece of wire, and investigate restistance by changing the length of wire, and see the PD across those lengths and the current to get Resistance

Question 13

how to determine resistivity from the values obtained from experiment

Answer 13

1. First draw line, it will be a linear line through origin. Y axis is resistance R, x axis is length/m
2. Get gradient
3. Gradient = R/L
4. Gradient x cross sectional area of wire = resitivity

Question 14

What is superconductivity

Answer 14

When material gets colder, their resistivity drops as expected. But then at a critical temperature the resistivity suddenly falls to 0.

Question 15

do components made of superconducting material have electrical resistance

And the effect of this

Answer 15

No, which is why huge amounts of current passes through them.

Question 16

What is the typical temperature at which wires become superconducting

Answer 16

4 Kelvin = -269 celcius

Question 17

What is the typical temperature for superconductors

Answer 17

4 Kelvin = -269 celcius

Question 18

What is the difference between resistance and resistivity

Answer 18

Resistivity is a property of a material that only changes if temperature changes. Measured in ohm metres

Resistance is dependant on resisitivity ie material, area and length of component. measured in ohms