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An electric water heater is used to make hot water for drinks - OCR Gateway - GCSE Physics - Question 19 - 2022 - Paper 1
Question 19
An electric water heater is used to make hot water for drinks. (a) The water heater is plugged into the mains supply and turned on. Explain why the temperature of ... show full transcript
Worked Solution & Example Answer:An electric water heater is used to make hot water for drinks - OCR Gateway - GCSE Physics - Question 19 - 2022 - Paper 1
Step 1
Explain why the temperature of the water increases
Answer
When the electric water heater is turned on, electrical energy is transferred from the mains supply to the water. This energy transfer occurs through the heating element, which uses electricity to generate heat. As the heating element warms up, it heats the water, causing an increase in thermal energy.
The energy stores of the water increase as the temperature rises. The kinetic energy of the water molecules increases, leading to a higher average kinetic energy, which is perceived as an increase in temperature.
Step 2
Calculate the energy required to increase the temperature of the water
Answer
To calculate the energy required to heat the water from 20°C to 95°C, we use the given formula:
- Mass of water = 10 kg
- Specific heat capacity of water = 4200 J/kg°C
- Change in temperature = 95°C - 20°C = 75°C
Substituting the values into the equation:
Calculating this gives:
Thus, the energy required to increase the temperature of the water is 3,150,000 J.