Energy Flashcards
(20 cards)
What are the types of energy stores with examples
Magnetic - compass
Thermal - human bodies
Chemical - food
Kinetic - car
Electrostatic - thunderclouds
Elastic potential - elastic band
Gravitational potential - kite
Nuclear - uranium
How is energy transferred
Mechanical work - a force moving an object through a distance
Electrical work - charges moving due to a potential difference
Heating - due to temperature difference caused electrically or by chemical reaction
Radiation - energy transferred as a wave
What is the conservation of energy
Energy can’t be created or destroyed, only transferred
What is the equation linking kinetic energy, mass and speed
Ek = ½ mv^2
Ek - kinetic energy, measured in J
m - mass, measured in kg
v - speed, measured in m/s
What is the equation linking GPE, mass, gravitational field strength and height
Ep = mgh
Ep - GPE, measured in J
m - measured in kg
g - gravitational field strength, measured in N/kg
h - height, measured in metres
What is the equation linking work done, force and distance
W = Fd
W - work done, measured in J
F - force, measured in N
d - distance, measured in m
What is the equation linking power, work done and time
P =W / t
P - power, measured in W
W - work done, measured in J
t - time, measured in s
How do you calculate efficiency
efficiency = useful energy transferred / total energy supplied
efficiency = useful power transferred / total power supplied
What is the difference between a conductor and insulator
Conductor - a material which allows charge to move easily through it
Insulator - a material that does not allow charge or heat to pass through it easily
Required practical : Measuring specific heat capacity
What is the method
Place the heater into the central hole at the top of the block
Place the thermometer into the smaller hole and put a couple of drops of oil into the hole to make sure the thermometer doesn’t get stuck
Wrap the block in an insulator
Record the temperature of the block
Connect the heater to the power supply and turn it off after ten minutes.
After ten minutes the temperature will still rise even though the heater has been turned off and then it will begin to cool
Record the highest temperature that it reaches and calculate the temperature rise during the experiment
What is energy needed for
Homes - cooking, heating and running appliances
Public services - schools and hospitals
Factories and farms - operating heavy-duty machines and production chains
Transport - buses, trains, cars and boats all need a fuel source and some trains and trams connect to an electricity supply
What are the patterns and trends in the use of energy resources
During the Industrial Revolution fossil fuels were used a lot
Electricity became convenient in the 20th century
More energy is used in the early evening than overnight
The impact of fossil fuels caused science and society to develop renewable energy
Some developed countries use nuclear power
What is the equation linking power, current and resistance
P = I2R
P - power, measured in W
I - current, measured in A
R - resistance, measured in Ω (Ohms)
What are the circuit rules
Current:
I1 = I2 = I3
Voltage:
V = V1 + V2
Resistance:
R = R1 + R2
What is the difference between an alternating and direct current
Alternate - current regularly changes direction
Direct - current flows in one direction
What is the mains electrical supply frequency and voltage
50 hertz
230 volts
What are the features of a plug
Cable grip - this holds the cable tightly in place so that wires do not become loose
Fuse - a canister with a thin wire that melts if the current gets too high
Neutral (blue) - completes the circuit (0 V). Left
Earth (yellow and green) - carries the alternating potential difference (230 V). Middle
Live (brown) - carries a current if there is a fault (0 V or 230 V). Right
What is the equation linking energy, power and time
E = Pt
E - energy, measured in J
P - power, measured in W
t - time, measured in s
What is the equation linking power, potential difference and current
P = IV
P - power, measured in W
I - current, measured in A
V - potential difference, measured in V
What do transformers do
Step up:
Voltage is increased from about 25,000 volts to 400,000 V causing the current to decrease. Less current means less energy is lost through heating the wire
Step down:
Reduces the voltage from the transmission voltage to the safer voltage of 230 V
