Question

1. A liquid of mass 250g is heated with an electric heater. Its temperature rises from 30°C to 80°C, the specific heat capacity of the liquid is 2000J/kg°C and the power rating of the heater is 500W. For how long was the heater used?
2. A solid metal of mass 2kg is heated using a heater of power 2kW for 5 minutes. Its final temperature becomes 400°C. Find the initial temperature of the metal. Specific heat capacity of the metal=1J/g°C.

Answer 1

Answer:

1) 50 seconds 2) 100°C

Explanation:

(Follows formula of Power=Energy/Time)

1) 500W x X = 2000J/kg°C x .25kg x 50°C

X = 50 seconds.

2) 2000W x 300s = 1000J/kg°C x 2kg x X

X = 300

Initial temperature => 400°C-300°C = 100°C