Ch - 6 (Energy Stores and Transfers) Flashcards
What is energy?
A property that must be transferred to an object in order to:
- work on
(or) - heat up the object
What is energy measured in?
Measured in Joules (J)
How many energy stores are there?
8 types
Name the energy stores.
- Kinetic
- Gravitational
- Elastic
- Electrostatic
- Magnetic
- Chemical
- Nuclear
- Thermal
What is the description of kinetic energy?
Energy an object has when it’s moving
What is the description of gravitational energy?
- Due to it’s position above the ground
- Gains gravitational energy when lifted
- Loses when its dropped
What is the description of elastic energy?
Energy stored in a stretched spring or elastic band
What is the description of electrostatic energy?
Due to force of attraction (or repulsion) due to charges.
What is the description of magnetic energy?
Due to Force of attraction (or repulsion) between 2 magnets
What is the description of chemical energy?
- Found in fuels, food, or in batteries
- transferred during chemical reactions.
What is the description of nuclear energy?
Contained within the nucleus of the atom
What is the description of thermal energy?
Due to its temp
What are the examples of energy transfers?
- Mechanical
- Electrical
- Heating
- Radiation
What is the description of mechanical energy?
When a force acts on a body
What is the description of electrical energy?
- Transfer of electric charge and electricity
- cell delivering to circuit
What is the description of heating energy?
Thermal energy transferred by conduction, convection, radiation
What is the description of radiation energy?
light and sound carry energy and can transfer this between 2 points.
what is kinetic energy (kinetic store) defined as?
The energy an object has as a result of its mass and speed
what does it mean if an object has kinetic energy?
Any object in motions has kinetic energy store.
What is the equation to calculate kinetic energy?
K.E = 1/2mv^2
K.E = in joules (J)
m = mass of object (kg)
v = speed (m/s)
What is gravitational energy (stored gravitational energy store) defined as?
The energy an object has due to its height in a gravitational field.
What does it mean if an object has gravitational energy?
- If object is lifted, energy will be transferred to its gravitational store.
- if an object falls, energy will be transferred away from its gravitational force.
What is the formula to calculate G.P.E?
/\Ep=mg/\h
/\Ep = change in GPE (J)
m = mass (kg)
g = gravitational field strength (N/kg)
/\h = change in height (m)
what does the law of conservation of energy state?
Energy cannot be destroyed, nor be created, it can only be transferred from one energy store to another
What does the law of conservation of energy state?
Total amount of energy in a closed system remains constant
What can be concluded by the law of conservation of energy state?
- Energy can be dissipated in surrounding by radiation (heat,light, or sound)
- Not useful energy (wasted energy)
How can energy stores and transfers be represented?
- Flow diagrams
- Sankey diagrams
What does the flow diagram show?
Stores and the transfers
what do the arrows on Sankey diagram show?
- Arrow pointing right shows used (useful output energy)
- Arrow pointing down (wasted energy)
What is the most important part of an arrow and what does it show?
Width of arrow is proportional to the amount of energy going to each store.
How can we find the total energy in?
Useful energy out + wasted energy =Total energy in
What does efficiency mean in general?
How well energy is transferred
define efficiency
The ratio of the useful power or energy transfer output from a system to its total power or energy transfer input.
What does it mean if an object has High efficiency?
Most energy transferred is useful
What does it mean if an object has low efficiency?
Most energy transferred is waste
How is efficiency represented?
Percentage
what is the formula for efficiency?
Efficiency = Useful energy output/total energy input x 100%
Define power
energy transferred per unit time
What is the formula for power?
Power = Energy transferred/Time
