Energy and Efficiency Flashcards

Flashcards based on lecture notes about energy, work, and efficiency.

Energy

Energy moves. It can be stored in different ways such as by heating, waves, electricity, or forces.

Kinetic Energy

Energy transferred as heat to the surroundings when something falls and hits the ground.

Conservation of Energy

Energy cannot be created or destroyed; it is always conserved, it just changes form.

Closed System

A system where nothing goes in or out; the total amount of energy stays the same, though it can move between different forms within the system.

Work

Done when a force makes something move. Formula: Work = Force x Distance

Friction

Turns work into thermal energy, causing things to get warmer when they rub together.

Gravitational Potential Energy

The gravitational potential energy of an object increases when it moves up and decreases when moving down.

Change in Gravitational Potential Energy Formula

ΔEp = mgΔh

Kinetic Energy

Also known as Ek, the energy of a moving object which depends on its mass and speed.

Kinetic Energy Formula

Ek = 1/2 mv²

Elastic Potential Energy

Energy stored in an elastic object when work is done on the object.

Elastic Potential Energy Formula

E = 1/2 ke², where e is the extension of the spring.

Useful Energy

Energy in the place we want it and in the form we need it.

Wasted Energy

Energy that is not useful and is transferred by an undesired pathway.

Efficiency Formula

Useful energy transferred by the device divided by the total energy supplied to the device (x100).

Sources of Energy Waste in Machines

Machines waste energy because of friction, air resistance, electrical resistance & noise.

Ways to Make Machines More Efficient

Using lubrication to reduce friction between moving parts

Common Energy Supplies Used at Home

Electricity and gas and/or oil

Uses of Electrical Appliances

Heating, lighting, making objects move, producing sound and visual images.

Power

Rate of transfer of energy

Power Equation

P = E/t

Efficiency of an Appliance Equation

(Useful power output / total power input) x 100%

Power Wasted by an Appliance Equation

Total power input - useful power output