Question
Question: Most of the times to determine the temperature in an electric furnace, thermometer containing thermo...
Most of the times to determine the temperature in an electric furnace, thermometer containing thermocouple is used. From the e.m.f. of the thermocouple the actual temperature of the substance is measured. The e.m.f. of the thermocouple varies with the centigrade temperature as follows:
e.m.f. = (0.2 t – 5 × 10–4 × t2) mV
The given thermometer is calibrated with the freezing point and the boiling point of water. If the thermocouple reads e.m.f. 105 mV in the blast furnace, then what is the temperature of the blast furnace in degree centigrade ?
A
1050C
B
7000C
C
157.50C
D
17000C
Answer
7000C
Explanation
Solution
At t = 0, e.m.f. = 0
At t = 100, e.m.f. = (20 – 5 × 10–4 × 104)mV
= 15 mV
\ rise in 1000C corresponds to e.m.f. = 15 mV
\ 105 mV e.m.f. corresponds to rise in
temperature 7000C