Answer:
68.25 minutes.
Explanation:
Power = Energy/time or
Power = Heat/time
P = Q/t....................... Equation 1
Q = Pt ........................ Equation 2
Where Q = quantity of heat, P = power, t = time.
Also,
Q = cm(t₂-t₁) ................. Equation 3
Where c = specific heat capacity of water, m = mass of water, t₁ = initial temperature of water, t₂ = final temperature of water.
substitute equation 2 into equation 3
Pt = cm(t₂-t₁) ............... Equation 4
make t the subject of the equation
t = cm(t₂-t₁)/P................ Equation 5
Given: P = 100 W, m = 1.3 kg, t₁ = 25 °C, t₂ = 100 °C.
Constant: 4200 J/kg.K
Substitute into equation 5
t = 1.3(4200)(100-25)/100
t = 409500/100
t = 4095 seconds
t = (4095/60) minutes = 68.25 minutes.
Hence the time it will take the water to reach boiling point = 68.25 minutes
