Question 20N.2.SL.TZ0.5b(i)

ALTERNATIVE 1

voltage across X$=2.3 «\mathrm{V}»$ ✓

voltage across R$«=4.0-2.3»=1.7 «\mathrm{V}»$ ✓

resistance of variable resistor $«=\frac{1.7}{0.020}»=85 «\mathrm{\Omega }»$ ✓

ALTERNATIVE 2

overall resistance $«=\frac{4.0}{0.020}»=200 «\mathrm{\Omega }»$ ✓

resistance of X $«=\frac{2.3}{0.020}»=115 «\mathrm{\Omega }»$ ✓

resistance of variable resistor $«=200-115»=85 «\mathrm{\Omega }»$ ✓