With reference to radioisotope thermoelectric generators (RTGs), consider the following statements : 1. RTGs are miniature fission reactors. 2. RTGs are used for powering the onboard systems of spacecrafts. 3. RTGs can use Plutonium-238, which is a by-product of weapons development. Which of the statements given above are correct ?
- A.1 and 2 only
- B.2 and 3 only
- C.1 and 3 only
- D.1, 2 and 3
Correct answer
Explanation
The correct answer is B, 2 and 3 only. RTGs power spacecraft using heat from the natural decay of plutonium-238; they are not reactors and involve no fission.
In an RTG, a radioactive isotope gives off heat as it decays on its own. Thermocouples convert that heat straight into electricity by the Seebeck effect, with no moving parts. Plutonium-238, with a half-life of about 88 years, is the usual fuel; it is made in nuclear reactors, and the United States first produced it alongside its nuclear weapons programme. RTGs have powered Voyager 1 and 2, Cassini, New Horizons and the Curiosity and Perseverance rovers, missions where sunlight is too weak or too unreliable for solar panels.
A is wrong because statement 1 is false: there is no chain reaction or fission in an RTG.
C is wrong for the same reason.
D is wrong because it includes the false statement 1.
Exam tip: RTG = radioactive decay heat + thermocouple (Seebeck effect); fuel Pu-238; used on deep-space probes.
Practice Questions
View allConsider the following statements :
Statement-I : Giant stars live much longer than dwarf stars.
Statement-II : Compared to dwarf stars, giant stars have a greater rate of nuclear reactions.
Which one of the following is correct in respect of the above statements?
- A.Both Statement-I and Statement-II are correct and Statement-II explains Statement-I
- B.Both Statement-I and Statement-II are correct, but Statement-II does not explain Statement-I
- C.Statement-I is correct, but Statement-II is incorrect
- D.Statement-I is incorrect, but Statement-II is correct
Show answer
Massive giant stars burn their fuel so fast that they live much shorter lives than dwarf stars, so Statement I is false and Statement II is true.
Read the full explanation →Which one of the following is a filter feeder?
- A.Catfish
- B.Octopus
- C.Oyster
- D.Pelican
Show answer
The oyster feeds by drawing water over its gills and straining out plankton and organic particles, which is filter feeding.
Read the full explanation →Consider the following :
1. Cashew
2. Papaya
3. Red sanders
How many of the above trees are actually native to India ?
- A.Only one
- B.Only two
- C.All three
- D.None
Show answer
Of the three, only red sanders is native to India; cashew and papaya were brought from the Americas. Red sanders (Pterocarpus santalinus) is endemic to the southern Eastern Ghats, mainly the Seshachalam and nearby hills of Andhra Pradesh.
Read the full explanation →Consider the following :
1. Butterflies
2. Fish
3. Frogs
How many of the above have poisonous species among them ?
- A.Only one
- B.Only two
- C.All three
- D.None
Show answer
Each of the three groups includes species that carry toxins in their bodies to deter predators. Butterflies: the Monarch butterfly feeds as a caterpillar on milkweed and stores its bitter cardiac glycosides, so birds that eat it fall sick; its bright orange colour is a warning.
Read the full explanation →The speed of the wind is measured by
- A.wind vane
- B.wind rose
- C.barometer
- D.anemometer
Show answer
An anemometer measures how fast the wind is blowing; its name comes from the Greek word anemos, meaning wind.
Read the full explanation →