energy transfer

What is the law of conservation of energy?

Energy cannot be created or destroyed, only transferred or changed from one form to another.

What is the unit for energy?

Joules

Give an example for kinetic energy stores.

Kinetic - A moving car

Give an example for gravitational potential energy stores.

Gravitational Potential - A book on a shelf

Give an example for elastic potential energy stores.

Elastic Potential - A stretched spring

Give an example for chemical energy stores.

Chemical - Food, batteries, fuel

Give an example for thermal energy stores.

Thermal - Boiling water in a kettle

Give an example for magnetic energy stores.

Magnetic - Magnets attracting/repelling

Give an example for electrostatic energy stores.

Electrostatic - Lightning

What is the mechanical pathway of transferring energy from one store to another?

When energy is transferred by a force moving something, e.g. pushing a box, a falling object or a stretched spring snapping back.

What is the electrical pathway of transferring energy from one store to another?

When energy is transferred by moving charges, e.g. a phone charging, a lamp plugged in or a TV working.

What is the heating pathway of transferring energy from one store to another?

When energy is transferred because of a temperature difference, e.g. a hot pan warming food, hands warming up near a heater or friction making things get hot.

What is the radiation pathway of transferring energy from one store to another?

When energy is transferred by waves, e.g. light from the Sun, heat from a fire or microwaves cooking food.

What is the order for describing energy transfers? (skill, not question)

store -> pathway -> store

Describe the energy transfer when using a torch.

chemical store (battery) -> electrical pathway -> thermal store

Describe the energy transfer in a moving car.

chemical store (fuel) -> mechanical pathway (engine turning wheels) -> kinetic + thermal store

Describe the energy transfer in the sun warming the earth.

nuclear store (energy inside of the sun) -> radiation pathway -> thermal store

Describe the energy transfer in charging a phone.

chemical store (power bank/mains) -> electrical pathway -> chemical store (battery)

What does it mean if energy is useful or wasted?

Useful energy is energy transferred to an intended purpose (e.g. light from a bulb), while wasted energy is energy dissipated to the surroundings, usually as unwanted thermal energy.

What is the useful energy in cars?

Useful - Kinetic

What is the wasted energy in cars?

Wasted - Thermal

What is meant by the dissipation of energy?

Energy is dissipated when it spreads out into the surroundings, usually as thermal energy, and becomes harder to use.

Why is saying 'Shut the door, as you'll let the cold in,' a wrong statement?

Cold air cannot move in. It is the heat that dissipates into the surroundings making the air inside feel colder. The longer the door is open, the more heat that escapes.

What is internal energy?

The energy stored in the movement of particles. Sometimed called thermal or heat energy.

What does the amount of thermal energy stored in something depend on?

The amount of thermal energy stored in something depends on its temperature, the material it is made from and its mass.

Why do you not get burned by sparklers?

The sparks do not store enough internal energy to burn you.

What is the difference between a conductor and an insulator?

A conductor is a material that lets electricity or heat flow through it easily. An insulator is a material that does not let electricity or heat flow through it easily.

In what ways can energy be transferred by heating?

Evaporation, radiation, conduction and convection.

What do all hot things emit?

Infrared radiation. The hotter the object, the more infrared radiation it emits. When radiation hits something, it can be absorbed or reflected.

What is radiation?

The transfer of energy in the form of waves.

How does conduction work?

Conduction is the transfer of thermal energy, through a solid and to a lesser extent a liquid or gas, by particles colliding. When a solid is heated, the particles vibrate more. These vibrations are passed through the solid and energy is transferred through metals this way.

How does convection work?

Energy is transferred through fluids by convection. When part of a fluid is heated it expands and becomes less dense then the fluid around it. It floats upwards through the remaining fluid. Cooler fluid moves in to take its place and a convection current forms.