L14 - resistance in a wire

Question 1

as you increase the length of the wire the resistance increases. why?

Answer 1

electrons in long wire collide with fixed ions more often.

Question 2

explain crocodile clip assessment (include one risk).

Answer 2

• crocodile clips moved along wire, increase length by 10cm.
• current (ammeter) and p.d (voltmeter) used to calculate resistance as the length of wire increases using equation ‘V=IR’, rearranging it to ‘R=V/I’.
• power supply must be switched off after every recording to prevent wire from burning which can also burn student’s skin if come into contact.
• resistance plotted on a dotted graph, resistance (Ω) on y-axis and length of wire (cm) on x-axis.
• directly proportional correlation.