A carbon resistor marked 560Ω is connected across a variable d.c. power supply. The supply voltage is gradually increased until the ammeter in series shows a steady reading of 25mA.
(i) Calculate the supply voltage at this instant.
(ii) The voltage is now adjusted so that the current decreases by 40%. Calculate the new current and the corresponding supply voltage.
(iii) For both situations calculate the value of resistance using your results and comment briefly on whether the resistor maintains a constant resistance as expected.