Energy Transfers

Flashcards covering energy transfers, stores, systems, cnservation of energy, and other related concepts for exam preparation.

What are the seven types of energy stores?

Thermal, Kinetic, Electrostatic, Chemical, Elastic Potential, Gravitational Potential, Nuclear.

What does the thermal energy store imply about an object?

The higher the store, the hotter the object.

What is the definition of kinetic energy?

Energy held by an object in motion.

What is electrostatic energy?

Energy stored when charged objects interact.

What does chemical energy refer to?

Energy stored in bonds that can be released in reactions.

When is elastic potential energy present in an object?

When the object has been deformed or changed shape.

What happens to gravitational potential energy when an object is raised?

It is stored as gravitational potential energy.

What is nuclear energy?

Energy stored in the nucleus of an atom, released during decay.

What is the mechanism for magnetic energy transfer?

Polar or magnetic objects interact with one another.

How can energy stores quantitatively change?

They can increase, decrease, or stay the same.

What is mechanical work in energy transfer?

When force acts on an object to transfer energy.

What does radiation refer to in energy transfer?

Energy transferred by electromagnetic waves.

How does heating transfer energy?

It transfers energy from a hotter object to a colder one.

What is electrical energy transfer?

Transfer of energy through electric currents.

What is a system in terms of energy transfers?

A group of objects that interact with each other.

What indicates a system is in equilibrium?

Nothing changes within the system.

What is an open system?

A system that allows exchange of matter and energy with the surroundings.

What is a closed system?

A system that can exchange neither matter nor energy with the surroundings.

What does the conservation of energy principle state?

Energy can be transferred or transformed but cannot be destroyed.

What happens to gravitational potential energy when a cat falls from a tree?

The cat’s gravitational potential energy decreases as it falls.

What work is done when burning fuel to heat water?

The fuel does heating work on the water.

What energy store decreases when a car goes uphill?

The chemical energy of the fuel.

What is the equation for gravitational potential energy?

GPE = mass x gravitational field strength x change in height.

What does the strength of the gravitational field on Earth approximate to?

9.8 N/Kg.

What is the equation for kinetic energy?

KE = mass x speed squared / 2.

In Hooke's Law, what is the relationship between force and extension?

Force is directly proportional to extension.

What is work done in energy transfer?

Energy transferred to an object by the action of a force moving it through distance.

What is the formula for work done?

Work done = Force x Distance travelled.

How do you calculate elastic potential energy from a spring?

Ee = 1/2 k e^2.

What is power in terms of work?

Power is the rate at which work is done.

How is power calculated?

Power = Work done / Time.

What is the daily energy usage of a fridge that draws 150W?

E = 12,960,000 J or 13 MJ.

What does 82% efficiency in a fridge mean?

It means 82% of the energy is effectively used to cool the contents.

How do you calculate efficiency?

Efficiency = useful energy output / total energy output.

What is the useful energy output for a fridge using 13 MJ of total energy?

10.6 MJ.

Why is Hooke's law significant in the study of springs?

It describes the elastic behavior of springs under force.

What factors determine the amount of gravitational potential energy required to lift an object?

Mass of the object, gravitational field strength, and height moved.

How does energy dissipate during transfers?

Some energy may be lost to surroundings as thermal energy.

Why is understanding energy stores and transfers important?

It helps in analyzing physical systems and their efficiencies.

What is a practical example of gravitational potential energy being converted to kinetic energy?

A cat falling from a tree, where GPE is converted to KE.

What is the initial assumption when calculating energy transfers?

Energy is assumed to come from one store and transfer to another.

What role does friction play in energy transfers?

Friction can cause energy to dissipate, often as heat.

In the context of energy, what does the term 'dissipated' mean?

Energy that is lost to the surroundings and not used for work.

What is the consequence of a system operating in a non-equilibrium state?

Energy transfers and changes will occur until equilibrium is restored.

Explain the concept of power in the context of machines.

Power indicates how fast a machine does work or converts energy.

What type of system would be used to study an isolated gas?

A closed system where no energy or matter is exchanged with surroundings.

How do electric appliances achieve efficiency?

By maximizing useful output and minimizing energy wastage.

What is the significance of the 24-hour measurement in power usage calculations?

It allows for understanding daily energy consumption patterns.

Describe what happens thermally to an object when it is heated.

Energy is transferred from a source, increasing the object's thermal energy.

What is the work done by a force of 10N moving an object 5m?

50 Joules (Work = Force x Distance).