1: Energy Flashcards
What is a system
A system is an object or a group of objects
State the equation for calculating kinetic energy
E = 1/2mv²
E (k): kinetic energy (Joules, J)
m: mass (Kilograms, kg)
v: velocity (meters per second, m/s)
State the equation for calculating elastic potential energy
E = 1/2ke²
E(e): elastic potential energy (Joules, J)
k: spring constant (newtons per metre, N/m)
e: extension (metres, m)
State the equation for calculating gravitational potential energy
E = mgh
E (gpe): gravitational potential energy (joules, J)
m: mass (kilograms, kg)
g: gravitational field strength (newtons per kilogram, N/kg)
h: height (metres, m)
State the equation for calculating change in thermal energy
ΔE = mc Δ θ
ΔE: change in thermal energy (joules, J)
m: mass (kilograms, kg)
c: specific heat capacity (joules per kilogram per degrees Celsius, J/kg°C)
State the equation for calculating power
P = E/t
(or)
P = W/t
P: power (watts,W)
E: Energy transfered (joules, J)
W: work done (joules, J)
t: time (seconds, s)
State the law of conservation of energy
Energy can be transferred usefully, stored or dissipated, but not created or destroyed
State the equation for calculating efficiency
Efficiency = useful output energy transfer / total input energy transfer
(or)
Efficiency = useful power output / total power input
State the main sources of renewable energy
Nuclear, bio-fuel, wind hydroelectricity, geothermal, tidal, solar and wave.
Required practical activity 14 (Pt1): What apparatus is required to investigate the specific heat capacity of different metals?
- Three metal blocks, one copper, one iron, one aluminium, each with two holes for a thermometer and heater.
- Some insulation to wrap round the blocks
- A thermometer
- A pipete to put water in the thermometer hole.
- A 12V immersion heater (30 - 110W)
- A 12V power supply
- An ammeter and a voltmeter
- Five connecting leads
- A stopwatch or stopclock
- A balance
Required practical activity 14 (Pt2): State a method you could use to investigate the specific heat capacity of different materials.
1: Measure and record the mass of the copper block in kg.
2: Wrap the insulation around the block
3: Place the heater in the larger hole in the block
4: Connect the ammeter, power pack and heater in series
5: Connect the voltmeter across the heater.
6: Use the pipette to put a small amount of water in the other hole.
7: Put the thermometer in this hole.
8: Set the power pack to 12V. Switch on the power pack to turn on the heater
9: Record the ammeter and voltmeter readings. These shouldn’t change during the experiment.
10: Measure the temperature and start the stopclock.
11: Record the temperature every minute for 10 minutes. Record these results in a table.
12: Calculate the power of the heater in watts
Power in watts = potential difference in volts x current in amps
13: Calculate the energy transferred (Work done) by the heater.
Energy transferred = power of heater x time in seconds. Record these results in the table.
14: Plot a graph of temperature against work done.
15: Draw a line of best fit
(Take care as the beginning of the graph may be curved)
16: Calculate the gradient of the straight part of the graph
Change in y / Change in x
17: Calculate the heat capacity of the copper block is calculated using:
1 / gradient
(The amount of energy needed to increase temperature by 1 degree.
18: Calculate the specific heat capacity of the block using:
Change in thermal energy = mass x specific heat capacity x temperature change
19: Repeat the experiment for blocks made from aluminium and iron.
