Physics
Grade-9
Easy
Question
A television that is 83% efficient provides 6000 J of useful energy. How much energy does it consume?
- 7229kJ
- 7229 J
- 7500 J
- 7400 J
Hint:
- Efficiency (%) = (useful energy output ÷ energy input) × 100
The correct answer is: 7229 J
- Efficiency (%) = (useful energy output ÷ energy input) × 100
Related Questions to study
Physics
Some homes are still heated by hot water boiler furnaces. The components of the system are an oil tank, a furnace, water pipes and radiators. The furnace burns the oil from the storage tank. The heat released is used to heat water which is then pumped to radiators throughout the house. A diagram is shown below.
If all the heat from the combustion was used to heat the water, the system would be 100% efficient. However, some heat is lost in the furnace exhaust and some is lost from the pipes delivering the water to the radiators.
One litre of oil delivers 48 000 kJ of energy. 7 600 kJ are lost to the exhaust, and 900 kJ are lost in transporting the hot water to the radiators. Determine the efficiency of this heating system.
Some homes are still heated by hot water boiler furnaces. The components of the system are an oil tank, a furnace, water pipes and radiators. The furnace burns the oil from the storage tank. The heat released is used to heat water which is then pumped to radiators throughout the house. A diagram is shown below.
If all the heat from the combustion was used to heat the water, the system would be 100% efficient. However, some heat is lost in the furnace exhaust and some is lost from the pipes delivering the water to the radiators.
One litre of oil delivers 48 000 kJ of energy. 7 600 kJ are lost to the exhaust, and 900 kJ are lost in transporting the hot water to the radiators. Determine the efficiency of this heating system.
PhysicsGrade-9
Physics
A simple diagram of a Hydro-Electric System is shown below
why all the energy from the water flowing into the turbine is not transformed into electrical energy.
A simple diagram of a Hydro-Electric System is shown below
why all the energy from the water flowing into the turbine is not transformed into electrical energy.
PhysicsGrade-9
Physics
An electrician installs patio lights in a back yard. Which of the following will decrease the efficiency of the wiring system to the back yard?
1- Bury the extension cord very deep down underground.
2- Use a short extension cord.
3- Use a long extension cord.
4- Use compact fluorescent light bulbs
An electrician installs patio lights in a back yard. Which of the following will decrease the efficiency of the wiring system to the back yard?
1- Bury the extension cord very deep down underground.
2- Use a short extension cord.
3- Use a long extension cord.
4- Use compact fluorescent light bulbs
PhysicsGrade-9
Physics
20 joules of energy are transformed into light, how much energy is dissipated as heat out of 40J given in.
20 joules of energy are transformed into light, how much energy is dissipated as heat out of 40J given in.
PhysicsGrade-9
Physics
Which glows brighter?
Which glows brighter?
PhysicsGrade-9
Physics
Total current is the sum of the current across each resistor in
Total current is the sum of the current across each resistor in
PhysicsGrade-9
Physics
Total current is the same across each resistance in
Total current is the same across each resistance in
PhysicsGrade-9
Physics
Your heating system is 45 percent energy efficient. The total useful output energy is 9000 kWh.
Changing the insulation would increase your house to 85 percent energy efficient. The cost to change the insulation is 131776 Rs. The cost of heating is 7 Rs/ kWh. How much time will it take to recover your investment?
Your heating system is 45 percent energy efficient. The total useful output energy is 9000 kWh.
Changing the insulation would increase your house to 85 percent energy efficient. The cost to change the insulation is 131776 Rs. The cost of heating is 7 Rs/ kWh. How much time will it take to recover your investment?
PhysicsGrade-9
Physics
A particular chemical process has an energy efficiency of only 3.00%. To complete this large-scale chemical process, 140,000 J of energy is input. What is the useful energy output of this process?
A particular chemical process has an energy efficiency of only 3.00%. To complete this large-scale chemical process, 140,000 J of energy is input. What is the useful energy output of this process?
PhysicsGrade-9
Physics
A construction worker puts 20 J of energy in to one strike of his hammer on the head of a nail. The energy transferred to the act driving the nail in to the wood is 8.0 J. What is his efficiency of hammering?
A construction worker puts 20 J of energy in to one strike of his hammer on the head of a nail. The energy transferred to the act driving the nail in to the wood is 8.0 J. What is his efficiency of hammering?
PhysicsGrade-9
Physics
A technician examines different electrical devices to determine the one that is the most energy efficient. While conducting a test, he notes that one of these devices consumes 650 000 J of energy and loses 315 000 J at the same time. What is the energy efficiency of this device?
A technician examines different electrical devices to determine the one that is the most energy efficient. While conducting a test, he notes that one of these devices consumes 650 000 J of energy and loses 315 000 J at the same time. What is the energy efficiency of this device?
PhysicsGrade-9
Physics
The table below has three different hairdryer models. Which is the least energy-efficient model?
The table below has three different hairdryer models. Which is the least energy-efficient model?
PhysicsGrade-9
Physics
An oven consumes 525 kWh of energy to provide 386 kWh of useful energy. What is its percentage efficiency?
An oven consumes 525 kWh of energy to provide 386 kWh of useful energy. What is its percentage efficiency?
PhysicsGrade-9
Physics
A television that is 83% efficient provides 5200 J of useful energy. How much energy does it consume?
A television that is 83% efficient provides 5200 J of useful energy. How much energy does it consume?
PhysicsGrade-9
Physics
A computer that is 87% efficient consumes 475 kWh of energy. How much useful energy does it provide?
A computer that is 87% efficient consumes 475 kWh of energy. How much useful energy does it provide?
PhysicsGrade-9
