Answers to GCSE Efficiency

Answers to GCSE Efficiency

Answers to Practice Questions

1.The electric motor in a fan will transfer 300J of chemical energy mechanically to 225J of kinetic energy, the remaining 75J of energy is transferred by radiation to the thermal energy store of the surroundings. Calculate the efficiency of the fan.

Input energy = 300J,

Useful output energy = 225J

Wasted output energy = 75J

An example of an efficiency calculation with full workings.
2. A wind turbine will transfer 1.0 x 106J of kinetic energy electrically into 600,000J of chemical energy to charge up a battery. The remaining energy is transferred by radiation to the thermal energy store of the surroundings. Calculate the efficiency of the wind turbine.
Example of an efficiency calculation, with full working out.
3. The energy used to increase the temperature of 1kg of water in a kettle is 2 x 106J. The kettle has a rated efficiency of 80%.
Calculate the input energy that the kettle requires.

Efficiency = 80%

Useful output energy = 2 x 106J
4. An electric motor uses a power of 150W to raise an object in height. 100J of work is done on the object over 0.8 seconds. Calculate the efficiency of the electric motor.

Input power = 150W
Back to efficiency
physics worksheet

Energy stores and systems notes and questions

Real life energy transfers

Kinetic energy

Gravitational potential energy

Elastic Potential energy

Changes in energy, Specific heat capacity

Power

Conservation of Energy

Work done

Conduction

Wasted energy transfers

Efficiency

Energy Resources

Wind and Solar

Coal, Oil and Natural Gas

Nuclear Power

Biofuels

Hydroelectric, Wave and Tidal

Circuit Symbols

Electric Current and Charge

Potential difference, Current and Resistance

Resistors

Thermistors and Light Dependent Resistors

Series Circuit

Parallel Circuits

Series Circuit Calculations

Parallel Circuit Calculations

Alternating and Direct Electrical Circuits

Mains Electricity

Earth wire

Fuses

Electrical Power

Energy Transfer in Circuits

Power of Appliances

National Grid

Static Charge

Static Electricity

Static Electricity and Forces

Static Electricity and Sparking

Electric Fields

Electric Fields and Objects

Density

Measuring Density

States of Matter

Changes of state

Internal Energy

Specific Heat Capacity

Latent Heat

Specific Latent Heat

Heating and Cooling Curves

Specific heat capacity compared to Specific latent heat

Motion of gas particles 

Gas Pressure and Volume

Doing work on gases

Structure of the Atom

Absorption and Emission of EM Radiation

Mass Number and Atomic Number

Isotopes

Ionisation

JJ Thomson and Plum pudding model

Ernest Rutherford and the Nuclear Model

Niels Bohr changing the Nuclear Model

Discovering the Proton and Neutron

Radioactive Decay

Measuring radiation from radioactivity

Radiation types and properties

Random nature of radioactive decay

Half life

Half life calculations

Radioactive contamination or irradiation

Hazards of contamination and irradiation

Studies on the effects of radiation on humans

Background Radiation

Different half lives of radioactive isotopes

Uses of nuclear radiation

Nuclear Fission

Nuclear Fission Chain Reaction

Writing nuclear fission equations

Drawing and interpreting nuclear fission diagrams

Nuclear Fusion

Scalar and Vector Quantities

Contact and Non Contact Forces

Describing interactions of forces and objects

Gravity

Measuring Weight

Calculating Weight

Resultant Forces

Free body diagrams

Free body diagrams part 2

Resolving Forces

Forces and Equilibrium

Finding the resultant force, using the parallelogram rule

Finding the resultant force, using the parallelogram rule part 2

Work done and Forces

Forces and Elasticity

Hooke’s Law

Calculating Spring Constant

Using Force-extension graphs

Linear and Non linear force extension graphs

Work done and elastic potential energy

 

Accordion Content
Accordion Content
Accordion Content
Accordion Content
Power = energy transferred/time