RESISTANCE AND RESISTIVITY

Question 1

What will depend on getting a particular potential difference?

Answer 1

The resistance of the component

Question 2

State the equation for resistance

Answer 2

R=V/I

Question 3

What is the SI unit for resistance?

Answer 3

Ohms

Question 4

Define one Ohm

Answer 4

If a potential difference of 1V make a current of 1A flow through it

Question 5

Name 3 things that determine the resistance.

Answer 5

1) Length- The longer the wire the more difficult it is to make current flow.
2) Area- The wider the wire the easier it will be for electrons to pass along it.
3) Resistivity- This depends on the material the wire’s made from.

Question 6

State the equation linking resistance and resistivity

Answer 6

R=pL/A

Question 7

What is the resistivity like in a conductor?

Answer 7

Very small

Question 8

Define resistivity

Answer 8

Resistivity of a material is the resistance of a 1m length with a 1m^2 cross sectional area.

Question 9

What are the units for resistivity?

Answer 9

Ohm metres

Question 10

What is the resistivity of copper?

Answer 10

1.72 x 10^-8

Question 11

What is Ohms law?

Answer 11

Provided the temperature is constant, the current through an ohmic conductor is directly proportional to the potential difference across it

Question 12

Describe 3 things on the graph current against potential difference for Ohms Law

Answer 12

1) Doubling the P.D. doubles the current
2) Resistance is constant
3) External factors will have a significant effect on the resistance, like temperature

Question 13

How would you measure the diameter of a piece of wire?

Answer 13

By using a micrometer