1. A, primarily consisting of B, is considered an environmentally friendly fossil fuel due to its low emissions. In addition to its use in heating and electricity generation, it is increasingly used as an alternative fuel in vehicles, known as C.
Identify A, B and C in this sentence.
a) A: Liquefied petroleum gas (LPG); B: Propane; C: Compressed Natural Gas (CNG)
b) A: Natural gas; B: Methane; C: Compressed Natural Gas (CNG)
c) A: Petroleum; B: Gasoline; C: Synthetic Natural Gas (SNG)
d) A: Diesel; B Propane; C: Compressed Natural Gas (CNG)
Answer: b) A is natural gas, which primarily consists of methane (B). Natural gas is a clean-burning fossil fuel.
Natural gas, when used as an alternative fuel in vehicles, is known as compressed natural gas (C, CNG). CNG is a popular alternative to gasoline and diesel in many vehicles due to its lower emissions and environmental benefits.
2. In the following question, you will find an assertion and a reason. Select the appropriate option that applies.
Assertion: Control rods made of materials like boron are used in nuclear reactors to regulate the rate of nuclear fission.
Reason: Control rods absorb excess neutrons and help maintain a controlled chain reaction.
a) Both the assertion and reason are correct, and the reason explains the assertion.
b) Both the assertion and reason are correct, but the reason does not explain the assertion.
c) The assertion is correct, but the reason is incorrect.
d) The assertion is incorrect, but the reason is correct.
Answer: a) Assertion correctly states that control rods made of materials like boron are used in nuclear reactors to regulate the rate of nuclear fission. These control rods are inserted or withdrawn from the reactor core to control the number of neutrons available for further fission reactions. The reason accurately explains the assertion as when control rods are inserted, they absorb excess neutrons, reducing the rate of fission and thus controlling the chain reaction.
3. Fuel R has a calorific value of 70 kJ/g and an ignition temperature of 25oC. Fuel S has a calorific value of 65 kJ/g and an ignition temperature of 35oC. Which fuel is a better overall choice for practical use, considering both energy content and ease of ignition?
a) Fuel R
b) Fuel S
c) Both fuels are equally suitable
d) It cannot be determined from the given information
Answer: a) A higher calorific value (70 kJ/g for Fuel R) indicates that Fuel R can produce more energy per unit mass when burned compared to Fuel S (65 kJ/g). This is an advantage in terms of energy content.
A lower ignition temperature (25oC for Fuel R) means that Fuel R can ignite at a lower temperature, making it easier to start the combustion process compared to Fuel S (35oC). This is an advantage in terms of ease of ignition.
Considering both factors, Fuel R is the better overall choice because it can release more energy and start burning at a lower temperature, which is desirable in most practical scenarios.
4. A science class wants to compare the effectiveness of different solar cookers. They set up three types of solar cookers: box-type, parabolic reflector, and evacuated tube cookers. Which type of cooker would you expect to reach the highest cooking temperature, and why?
a) Box-type cooker, as it traps and concentrates heat efficiently.
b) Parabolic reflector cooker, as it reflects sunlight directly onto the food.
c) Evacuated tube cooker, as it isolates heat better than other types.
d) All three cookers would reach similar temperatures under sunlight.
Answer: b) Parabolic reflector cookers are designed to focus and concentrate sunlight directly onto the cooking surface. The parabolic shape of the reflector allows it to capture sunlight from a wide angle and direct it towards a single focal point, where the cooking vessel or food is placed. This concentrated sunlight generates very high temperatures at the focal point, making the parabolic reflector cooker capable of reaching the highest cooking temperature among the three types of solar cookers.
5. A geothermal power plant generates 300,000 kilowatts (kW) of electrical energy using underground reservoirs. Due to resource limitations, the plant can only operate at 60% capacity. If the plant runs continuously for 24 hours, how many megawatt-hours of electricity does it produce daily?
a) 120 MW
b) 432000 MW
c) 4320 MW
d) 2250 MW
Answer: c) To determine the daily electricity generation in megawatt-hours (MWh), the following steps can be followed:
Convert the power output from kilowatts (kW) to megawatts (MW) because 1 MW is equal to 1000 kW:
Power output = 300,000 kW ÷ 1000 = 300 MW
Consider the power plant's operational capacity, which is 60%:
Effective power output = 300 MW × 0.60 = 180 MW
Compute the daily energy production by multiplying the effective power output by the number of hours in a day (24 hours):
Daily energy production = 180 MW × 24 hours = 4,320 megawatt-hours (MWh)
Hence, when the geothermal power plant operates at 60% capacity and runs continuously for 24 hours, it generates 4,320 MWh of electricity daily.
