Quiz 1: Energy conversion and Power plant

The 1st law of thermodynamics is about energy conservation; energy cannot be created or destroyed.

• True

• False

Which of the following is a Fossil / traditional energy source?

• Hydrogen.

• Coal

• Solar

• Biomass

In a thermal power plant, which component converts steam energy into mechanical energy?

• Boiler.

• Turbine.

• Generato.

• Condenser.

Which of the following is a renewable power source?

• Solar

• Wind

• desiel

• coal

A closed system cannot exchange mass with its surroundings

• True

• False

An isolated system cannot exchange mass or energy with its surroundings

• True

• False

A combustion efficiency of 80%, how much of the amount of heat released during the combustion of gasoline has a heating value LHV=44000 kJ/kg.

• 35200 kJ/kg

• 50000 kJ/kg

• 44000 kJ/kg

• 88000 kJ/kg

What is the efficiency of a cooking appliance in this scenario, given that the energy supplied to the appliance is 5 kW and the energy used and transferred to the food is 3 kW?

• 0.6

• 0.5

• 08

• 1

Find the mechanical efficiency of a fan, the ratio of the mechanical energy of air (mv²/2 ) to the mechanical power input of 50 W.

• 0.74

• 0.77

• 0.8

• 0.9

The efficiency of open burners is determined to be 73% for electric units and 38% for gas units. Consider the energy used of 1.46 kW in both burners, at a location where the unit costs of electricity and natural gas are $0.09/kWh and $0.041/kWh, respectively. Determine the rate of energy input for both burners and the unit cost of utilised energy for both electric and gas burners.

• Energy input for electric burner=.......... kW.

• Energy input for gas burner= ...... kW.

• Cost for the using electric burner= ..... $/kWh

• Cost for the using gas burner= ..... $/kWh

Answer explanation

Energy input for electric burner= 1.46/0.73= 2 kW.

Energy input for gas burner= 1.46/0.38= 3.84 kW.

Cost for the using electric burner= 0.09/kWh / 0.73= 0.123 $/kWh

Cost for the using gas burner= 0.041kWh/0.38 0= 0.108 $/kWh