Unit 4 - Energy Flashcards
What is energy?
The capacity to do “work”.
Define thermal energy
Thermal energy: atoms possess thermal energy – the faster they move the greater it is
Define electrical energy
Electrical energy: possessed by charged particles, transferred as they move through a circuit
Define radiant energy
Radiant: travels via waves, no particles required
Define nuclear potential
Nuclear potential: the nucleus of every atom has stored energy which can be released via fissions, etc.
Define gravitational potential
Gravitational potential: a raised object has stored energy due to its position above some reference level
Define kinetic energy
Kinetic: every moving object has energy of motion – kinetic energy
Define elastic potential
Elastic: potential energy stored in objects that are stretched or compressed
Define sound energy
Sound: produced by vibration, travels by waves through a material to the receiver
Define chemical potential
Chemical potential: in chemical reactions, new molecules are formed and energy is released or absorbed
Explain work and its directions
When a force acts on an object and causes displacement, it is said that work is down.
Work is measured in Joules (J)
W = F x D (x cos0) – the angle between the applied force and the distance
- Positive - force and displacement are in the same direction
- Negative - force and displacement are in the opposite direction
- Zero - force is applied, but results in the displacement
Define total mechanical energy
Total Mechanical Energy: The sum of the gravitational potential energy and the kinetic energy.
Formula for Ep
Eg = mgh (mass x -9.8 x height), J
Formula for Ek
Ek = mv2/2, J
Explain mechanical efficieny
The ratio of useful energy provided by the device to the energy required to operate the device. For example, a lightbulb produces heat as well as light.
Efficiency = Eout/Ein x 100%
Energy in = the added force’s work, W = F x D
Energy out = potential energy, Ep = mgh
What is conduction?
- Process of heat transferring through a substance by the collision of atoms and electrons.
- Conduction occurs best in metals because electrons move more freely. This makes them good conductors of electricity.
- Allows temperature to flow from high to low temperatures.
What is convection?
- Transfer of heat by a circulating path.
- Hot air rises because it becomes less dense and cool air falls because it becomes denser.
What is radiation?
- Transfer of heat that requires no particles.
- Transferred via electromagnetic waves…
- Visible light
- Microwaves
- Radio waves
- Radar
- X rays
- Infrared rays
Thermal energy vs. Temperature
Thermal Energy
- Total kinetic and potential energy of the atoms or molecules of a substance.
- Depends on mass, temperature, nature, and state of a given substance.
Temperature
- Measure of the average kinetic energy of the atoms and molecules of a substance, which increases if the motion of the particles increases.
Define specific heat capacity:
Specific Heat Capacity: the amount of heat required to raise the temperature of 1.0 kg of that material by 1.0°C
Equation for heat transfer:
Q = m•c•∆T, J
Equation for heat exchange:
mhch∆Th + mccc∆Tc = 0
Work vs. Power
Work versus Power:
- Power is the rate at which WORK is done.
- For example, two individuals of the same mass and height can perform the same amount of work while running 100m, because work is distance x force.
- However, if one individual can complete the 100 m distance in a shorter period of time, they have more power, because to calculate power, work is divided by the time it takes to complete the work.
- Power is measured in Watts (W).
Power = Work/time, W
