resistance

Question 1

potential difference equation

Answer 1

current x resistance (V=IR)

Question 2

units for pd equation

Answer 2

pd-volts
current-amps
resistance-ohms

Question 3

what does resistance tell us?

Answer 3

the potential difference required to drive a current through a component

Question 4

what happens to the resistance of ohmic conductors at a constant temperature as the current is changed?

Answer 4

it stays the same

Question 5

what is directly proportional to current?

Answer 5

potential difference

Question 6

give examples of components where resistance changes depending on current

Answer 6

filament lamp
diode

Question 7

describe why resistance changes in a filament lamp

Answer 7

When a charge flows through, it transfers some energy to the thermal energy store of the filament which is designed to heat up. Resistance increases with temperature so as the current increases the filament lamp heats up more, and resistance increases.

Question 8

describe why resistance changes in a diode

Answer 8

the resistance depends on the direction of the current, so if the current is reversed the resistance is very high

Question 9

why does resistance increase?

Answer 9

when there is a temperature increase