A wire heating element made of nichrome is connected to a 230 V d.c
PHYSICS · Subjective · CBSE · Physics · Current Electricity · Current Electricity
Problem
A wire heating element made of nichrome is connected to a 230 V d.c. supply. At the instant of switching on, when its temperature is 25 °C, the current in the circuit is 5.0 A. After a short time the element reaches a steady temperature at which the current settles to 4.2 A.
For nichrome, the temperature coefficient of resistivity may be taken as 1.7 × 10⁻⁴ °C⁻¹ and is assumed constant over the temperature range involved.
(i) Determine the steady resistance of the element at the higher temperature.
(ii) Hence calculate the final temperature of the element.
(iii) Find the percentage change in power dissipated in the element between the initial moment and the steady state.
(iv) Explain briefly why the current decreases as the wire heats up even though the applied voltage remains constant.