Find the amount of electrical energy expended in raising the temperature of 50 litres of water by 75° C.To what height could a weight of 5000 kg be raised with the same expenditure of energy ? Assume that heater has an efficiency of 90% and the lifting equipment has an efficiency of 70%.

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**Problem Statement:**

Find the amount of electrical energy expended in raising the temperature of 50 liters of water by 75° C. To what height could a weight of 5000 kg be raised with the same expenditure of energy? Assume that the heater has an efficiency of 90% and the lifting equipment has an efficiency of 70%.

**Explanation:**

- **Electrical Energy Calculation:**
   - Determine the energy required to heat the water using the formula:
     \[
     Q = m \cdot c \cdot \Delta T
     \]
     where:
     - \( m \) is the mass of the water (50 kg for 50 liters, assuming the density is 1 kg/L),
     - \( c \) is the specific heat capacity of water (approximately 4.18 J/g°C),
     - \( \Delta T \) is the temperature change (75°C).

- **Efficiency Considerations:**
   - The heater’s energy input must account for its efficiency.
   - To find the actual electrical energy expended, divide the calculated energy by the heater efficiency (0.9).

- **Height Calculation:**
   - Using the remaining energy and considering the lifting equipment efficiency, calculate the height to which 5000 kg can be raised.
   - Use the gravitational potential energy formula:
     \[
     E = m \cdot g \cdot h
     \]
     where:
     - \( E \) is the useful energy output (after applying both efficiencies),
     - \( g \) is the acceleration due to gravity (approximately 9.81 m/s²),
     - \( h \) is the height.

This setup involves converting electrical energy into thermal energy and then using that energy to do mechanical work, taking into account the inefficiencies in each process.
Transcribed Image Text:**Problem Statement:** Find the amount of electrical energy expended in raising the temperature of 50 liters of water by 75° C. To what height could a weight of 5000 kg be raised with the same expenditure of energy? Assume that the heater has an efficiency of 90% and the lifting equipment has an efficiency of 70%. **Explanation:** - **Electrical Energy Calculation:** - Determine the energy required to heat the water using the formula: \[ Q = m \cdot c \cdot \Delta T \] where: - \( m \) is the mass of the water (50 kg for 50 liters, assuming the density is 1 kg/L), - \( c \) is the specific heat capacity of water (approximately 4.18 J/g°C), - \( \Delta T \) is the temperature change (75°C). - **Efficiency Considerations:** - The heater’s energy input must account for its efficiency. - To find the actual electrical energy expended, divide the calculated energy by the heater efficiency (0.9). - **Height Calculation:** - Using the remaining energy and considering the lifting equipment efficiency, calculate the height to which 5000 kg can be raised. - Use the gravitational potential energy formula: \[ E = m \cdot g \cdot h \] where: - \( E \) is the useful energy output (after applying both efficiencies), - \( g \) is the acceleration due to gravity (approximately 9.81 m/s²), - \( h \) is the height. This setup involves converting electrical energy into thermal energy and then using that energy to do mechanical work, taking into account the inefficiencies in each process.
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