 µ IB | Energy Sources

10 quick questions

10 minutes maximum! (can you do it in 5?)

1. Which of the following lists of energy sources are all classed as renewable resources?

• A. Coal, wind, nuclear.
• B. Nuclear, geothermal, tidal.
• C. Wave, Tidal, Hydroelectric.
• D. Natural gas, hydroelectric, tidal.

2. Which of the answers below gives the correct units used for specific energy and the energy density of a fuel?

Specific Energy Energy Density
A
J kg-1 J m-3
B
J m-3 J kg-1
C
W kg-1 W m-3
D
W m-3 W kg-1

3. A block of solid fuel X has twice the specific energy of fuel Y. In order to release the same quantity of energy on efficient burning, how much of fuel Y needs to be used?

• A. Twice the volume of fuel X
• B. Half the volume of fuel X
• C. Twice the mass of fuel X
• D. Half the mass of fuel X 4. A powerstation that is 40% efficient produces 12 MW of wasted thermal energy when in operation. What is the useful power output of the plant?

• A. 18 MW
• B. 15 MW
• C. 9 MW
• D. 8 MW

5&6. A small hydroelectric plant is rated as being only 20 % efficient. The energy output each second is shown in the sankey diagram below: 5. Which of the answers below best describes the missing labels X and Y?

X Y
A
Potential energy (16 kJ) Wasted thermal and kinetic energy (12 kJ)
B
Potential energy (20 kJ) Wasted thermal and kinetic energy (16 kJ)
C
Thermal (internal) energy (16 kJ) Potential energy (12 kJ)
D
thermal and kinetic energy (16 kJ) Potential energy (20 kJ)

6. The flow rate through the turbine and generator in a hydroelectric plant is dependent on a large reservoir of water. The pipe feeding the turbines is placed at the bottom of the reservoir. Which of the following variables will have no effect on the flow rate?

• A. The depth of the reservoir.
• B. The drop in height of the water flowing from the reservoir through the turbines.
• C. The width of the reservoir.
• D. The pressure at the bottom of the reservoir.

7&8. A wind turbine produces a power output of 0.1 MW.

7. What is the energy output over an hour in joules, assuming the power output is constant? 8. An identical design of wind turbine is nearby, in wind of the same velocity but with 3 times the diameter. If the efficiency of both turbines is the same, what is the output of the larger generator?

• A. 0.1 MW
• B. 0.3 MW
• C. 0.9 MW
• D. 5.4 MW

9. In a nuclear power station, what is the function of the moderator?

• A. To slow down neutrons to a suitable speed for fission to occur.
• B. To absorb nuetrons to prevent the chain reaction accelerating.
• C. To transfer thermal energy from the core to the secondary cooling system.
• D. To absorb neutrons and othe ionising radiation from the core for safety.