Given : E = 10 volts L = AB =100 cmThus potential difference A and C V_{AC} = \\dfrac{E}{AB}\ imes AC = \\dfrac{10}{100}\ imes 40 = 4 volts \ herefore V_{BG} = V_{PM} = V_{AC} =4 voltsUsing V_{BG} = 5- Ir where r =1\\Omega \ herefore 4 = 5 -I(1) \\implies I = 1 AThus resistance R = \\dfrac{V_{PM}}{I} = \\dfrac{4}{1} =4\\Omega