Energy Flashcards
what is energy?
the ability to do work
what is the law of conservation of energy?
energy cannot be created or destroyed; only transferred
what are the stores of energy?
kinetic
gravitational potential
thermal
elastic potential
chemical
nuclear
magnetic
electrostatic
how can energy be transferred?
heating
mechanically (force causes something to move)
waves (light+sound)
electrically (only if electricity is used)
what is a system?
an object or group of objects
what happens in a closed system?
there’s no net (overall) change to the amount of energy in the system
GPE equation
E=mgh
KE equation
E=1/2mv²
thermal energy equation
∆E=mc∆θ
what is specific heat capacity; c?
the amount of energy needed to raise 1kg of a substance by 1 °C
what is efficiency?
how good a device is at transferring energy usefully
efficiency equation
efficiency=useful power or energy output/total power or energy input
how do you improve efficiency?
insulation
lubrication
what is power?
rate of energy transfer
power equation
E=Pt
what is renewable energy?
a source that can be replenished as it’s used
examples of renewable energy sources
biofuel - plant matter waste
wind - wind current turbines
hydroelectric - dams of water= flood valley= gpe
geothermal - steam from hot ground
tidal - ke of tide (sea water)
solar - UV rays
waves - moving turbines connected to a generator
pros and cons of biofuel
pros
- carbon neutral
- reliable
cons
- plants have to be destroyed
pros and cons of wind
pros
- free
- safe for the environment
- no CO2 released
cons
- unreliable
- noise+sight pollution
- need LOTS to meet energy demand
- turbines=expensive
- kill birds
pros and cons of hydroelectric
pros
- safe for environment
- no fuel cost
- energy on demand
- no CO2 released
cons
- destroys habitats
- methane released
pros and cons of geothermal
pros
- no CO2 released
- no fuel cost
- good for envirionment
cons
- specific location needed
pros and cons of tidal
pros
- no CO2 released
- no fuel cost
cons
- requires a coast
pros and cons of solar
pros
- no CO2 released
- no fuel cost
cons
- panels= expensive
- unreliable= needs sunny weather
- max power?
pros and cons of waves
pros
- safe for environment
- no CO2 released
- no fuel cost
cons
- unreliable
what is non-renewable energy?
a source that cannot be replenished
examples of non-renewable energy sources
fossil fuels (oil, coal, gas) - remains of dead marine life
nuclear - unstable nuclei in atoms eg. uranium or plutonium
pros and cons of fossil fuels
pros
- give lots of energy=can meet high energy demand
- easy to use
- reliable
cons
- release CO2=enhance greenhouse effect
pros and cons of nuclear
pros
- give out the highest amount of energy
- reliable
- no CO2 released
cons
- toxic waste=very dangerous= safety equipment needed=expensive
- how to store waste
specific heat capacity practical
- measure mass of metal with a balance
- record start temp with a thermometer
- heat for 10 mins using a (emergent) heater
- record final temp with a thermometer
- measure energy used using a joulemeter
- use ∆E=mc∆θ to calculate shc
how to reduce energy waste
Lubrication
o Oil in a motor
o Reduces friction
o So less energy is lost (as heat) through friction
- Thermal Insulation
o Double Glazing
o Less useful thermal energy lost
