P1 Flashcards
(45 cards)
examples of energy stores?
thermal KE GPE EPE Chemical Magnetic Electrostatic Nuclear
how is energy transferred mechanically
by a force doing work
how is energy transferred electrically
by moving charges
ions/delocalised electrons
how is energy transferred by heating/radiation
by light or sound
what’s a system
an object or group of objects
what happens when the system changes
energy is transferred into or away from the system, between different objects or different types of energy stores
what’s a closed system
system where matter or energy can’t leave
net change of total energy is always 0
explain the energy transfer by heating in a kettle
energy is transferred to water (from kettle heating agent) by heating into the thermal energy store
temp. increases
define work done
another way of saying energy transferred
how can work be done
when a current flows
or by a force moving an object
explain how work is done when a ball is thrown upwards
initial force exerted by person to throw ball up does work
energy transfer from chemical energy store to KE energy store of the ball and arm
explain how work is done when a ball is dropped from a height
ball dropped from a height is accelerated by gravity- the force does work
causes energy ti transfer from ball’s GPE to KE store
explain how work is done when an object slows down (car)
friction between car’s brakes and its wheels does work as it slows down
energy transfer from wheels’ KE store to thermal store of surroundings
explain how work is done when a moving object (car) hits an obstacle/stationary object
when they collide, normal contact force does work
energy transfers from car’s KE tore to other stores e.g. elastic/thermal of obstacle and car body
some energy transferred as sound waves
what’s the KE equation?
KE = ½ x m x v²
(mass in kg)
(energy in J)
(speed in (m/s)²)
what’s the GPE equation?
GPE = m x g x h (energy in J) (mass in kg) (GFS in N/kg) (height in metres)
what’s the rule when there’s a falling object with no air resistance?
energy lost from GPE store = energy gained in KE store
what’s the EPE equation?
EPE = ½ x k x e²
(energy in J)
(spring constant in N/m)
(extension in metres)
what’s SHC
amount of energy needed to raise the temp. of 1kg of a substance by 1°C
what’s the SHC equation?
ΔE = m x c x ΔT (energy in J) (mass in kg) (SHC in J/kg°C) (temp. in °C)
explain SHC practical
1) get a block of a material (copper)
2) put 2 holes in it for heater and thermometer
3) measure block mass
4) wrap block in insulation layer to reduce energy transfer to surroundings
5) insert thermometer and heater
6) measure initial temp of block
7) set p.d. to 10V, turn on power supply and stop watch
8) current in circuit does work on heater, so energy electrically transferred from from power supply to heater’s thermal store by heating so temp increases
9) take readings every min for 10 mins, current doesnt change
10) after 10 readings calc power supplied and energy transfer to heater
define the term power
the rate at which energy is transferred/work is done
which equation links power and energy/work done?
power (Watts) = energy transferred OR work done (J)
——————————————————
time (secs)
how many Watts is 1 Joule per second?
1 Watt
