2.2 Resistance

Question 1

Potential difference

Answer 1

The energy supplied per unit charge

Question 2

What does a higher resistance mean

Answer 2

A larger potential difference is required to produce a current

Question 3

Ohm’s law

Answer 3

The current through a conductor is proportional to the potential difference across the conductor. The ratio of V to I / the resistance remains constant for all values of V and I

Question 4

Electrical resistance, R

Answer 4

The resistance of a conductor is the pd (V) placed across it divided by the resulting current (I) through it.
R = V / I
Unit:Ω (V A ^-1)

Question 5

Resistivity, ρ

Answer 5

The resistance, R, of a metal wire of length L and cross- sectional area A is given by R = ρL / A, in which ρ, the resistivity,
is a (at constant temperature) for the material of the wire. Unit: Ω m

Resistivity is a property that describes the extent to which a material opposes the flow of current through it

Question 6

Superconducting transition temperature, Tc

Answer 6

The temperature at which a material, when cooled, loses all its electrical resistance, and becomes super-conducting. Some materials (e.g. copper) never become superconducting however low the temperature becomes