A student is investigating the resistance of two resistance wires, XYXYXY and WZWZWZ, using a circuit similar to the layout of a standard wire resistance experiment. Wires XYXYXY and WZWZWZ are connected together at their left ends, XXX and WWW.
The student first records the potential difference VVV and current III for a length l=0.250 ml = 0.250\text{ m}l=0.250 m of wire XYXYXY:
V=1.05 V,I=0.35 A V = 1.05\text{ V}, \quad I = 0.35\text{ A} V=1.05 V,I=0.35 AThe student repeats the measurement for l=0.500 ml = 0.500\text{ m}l=0.500 m:
V=2.03 V,I=0.34 A V = 2.03\text{ V}, \quad I = 0.34\text{ A} V=2.03 V,I=0.34 AThe student notes the readings when the sliding contact is placed on wire XYXYXY at l=0.600 ml = 0.600\text{ m}l=0.600 m with no connection between YYY and ZZZ:
V1=2.30 V,I1=0.32 A V_1 = 2.30\text{ V}, \quad I_1 = 0.32\text{ A} V1=2.30 V,I1=0.32 AThe student then connects points YYY and ZZZ with a short wire, keeping the contact at l=0.600 ml = 0.600\text{ m}l=0.600 m:
V2=2.09 V,I2=0.58 A V_2 = 2.09\text{ V}, \quad I_2 = 0.58\text{ A} V2=2.09 V,I2=0.58 ASuggest two reasons why different students all carrying out this experiment carefully, with the same apparatus, may not obtain identical results.
132 exam-style questions on CIE IGCSE Physics 4.2.4a Resistance. Each one has a worked solution and a mark scheme showing where the marks go.