19.

(a) Redraw Fig. 48.45 adding suitable components which would enable a student to investigate how the resistance of the resistor, R, varies with current.

(b) Copy the axes below and sketch a graph of the results you would expect to obtain when the current is increased from 0 to 0.2 A, assuming the temperature of the resistor is constant. Label this line X.

(c) A second identical resistor is placed in parallel with R and the combined resistance is measured over the same range of current. Sketch a second graph on the same axes to show the results you would expect to obtain, assuming the temperature of the resistors is constant. Label this line Y.

(d) Explain the shapes and positions of lines X and Y.

Fig. 4B.45 R