A platinum resistance thermometer wire has a re... - JAMB Physics 2015 Question
A platinum resistance thermometer wire has a resistance of 70hms at 0°Cand 7.5 Ohms at 100°C. Calculate the temperature of the wire when the resistance is 7.2 Ohms
A
15°C
B
40°C
C
20°C
D
10°C
correct option: b
R0 = 7Ω , R1 = 7.2 Ω, R2 = 7.5 Ω, Tx = ?
[(X – T100°C) ÷ (R1 - R0)] = [(T100°C – T0°C) ÷ (R2 - R0)]
[(Tx – 0) ÷ (72 – 7)] = [(100 – 0) ÷ (7.5 – 7)]
Tx/0.2 = (100 ÷ 0.5)
Tx = [(0.2 × 100)] ÷ 0.5
= 20/0.5 = 40°C
[(X – T100°C) ÷ (R1 - R0)] = [(T100°C – T0°C) ÷ (R2 - R0)]
[(Tx – 0) ÷ (72 – 7)] = [(100 – 0) ÷ (7.5 – 7)]
Tx/0.2 = (100 ÷ 0.5)
Tx = [(0.2 × 100)] ÷ 0.5
= 20/0.5 = 40°C
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