## AQA GCSE Efficiency

**Efficiency**

**Efficiency** is a measure of how much of the **input energy** is transferred into **useful output** **energy**, or how much of the **input power** is transferred into **useful output power**.

**Efficiency and Sankey Diagrams**

You may have to **draw**, or **interpret** **sankey diagrams**.

Here is a guide to **Sankey diagrams:**

The** diagram **is** drawn **to** scale. **

On the **left** is the **input energy (4000J). Arrow **is** vertical, **every** tiny box **is worth** 100J, count along the arrow 40 boxes, so 4000J.**

On the **right** is the** useful energy** outputs **(2500J). Arrow** is** vertical, 25 **tiny** boxes along arrow, each box 100J, so 2500J.**

On the **bottom** is the **wasted energy outputs**. **(1500J). Arrow **is** horizontal, count **tiny** boxes along arrow, 15 boxes so 1500J. **

**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.

2. A wind turbine will transfer 1.0 x 10^{6}J 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.

3. The energy used to increase the temperature of 1kg of water in a kettle is 2 x 10^{6}J. The kettle has a rated efficiency of 80%. Calculate the input energy that the kettle requires.

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.

Absorption and Emission of EM Radiation

JJ Thomson and Plum pudding model

Ernest Rutherford and the Nuclear Model

Niels Bohr changing the Nuclear Model

Discovering the Proton and Neutron

Measuring radiation from radioactivity

Radiation types and properties

Random nature of radioactive decay

Radioactive contamination or irradiation

Hazards of contamination and irradiation

Studies on the effects of radiation on humans

Different half lives of radioactive isotopes

Nuclear Fission Chain Reaction

Writing nuclear fission equations