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Physics · Thermal · Specific heat capacity
Specific heat capacity of water
An immersion heater of known power heats a measured mass of water in an insulated beaker. The temperature rise after a known time gives the specific heat capacity using Q = mcΔT — and the difference between the calculated value and the true 4180 J/kg/K reveals how much heat is lost to the surroundings.
t = 0 s
V
12.0 V
I
4.0 A
P = VI
48 W
Mass
0.200 kg
ΔT
0.0 K
c (apparent)
—
Calculation
VIt = mcΔT
c = (V × I × t) / (m × ΔT)
Published value: 4180 J/kg/K. Difference is heat lost to beaker / surroundings / heater (~14 %).
Exam-style questions
1. Which equation links electrical input to heat produced?
2. Specific heat capacity is defined as:
3. The experimental c usually comes out HIGHER than 4180. Why?
4. 12 V × 4 A heats 200 g of water for 5 min. ΔT = 17 °C. Calculate c.