GCSE Physics Paper 2 (2)

Which element is often used as a nuclear fuel in fission reactors?

• Uranium-235

• Hydrogen

• Helium

• Iron-56

Answer explanation

In a nuclear fission reactor, uranium-235 is often used as the fuel.

A neutron is absorbed into a ²³⁵U nucleus, turning it into ²³⁶U which is very unstable.

The nucleus then splits into two daughter nuclei and at the same time it releases other high energy particles.

Neutrons from the splitting of one uranium-236 nucleus can collide with other uranium nuclei and cause further fission reactions.

What term describes this sequence of reactions?

• Reaction force

• Chemical reaction

• Chain reaction

• Reversible reaction

Answer explanation

When neutrons from the fission of one ²³⁶U nucleus collide with other uranium nuclei, they cause further fission reactions, and this is called a chain reaction.

If these reactions are not slowed down, the reaction becomes uncontrollable and this is what occurs in a nuclear fission bomb (an atomic bomb).

The photograph shows the cloud produced by the explosion of a fission bomb over Nagasaki in Japan, at the end of the Second World War.

Next

In what form is the signal passed to the loudspeaker?

• Changing current

• Morse code

• Sound waves

• Changing magnetic field

Which type of current only flow in one direction?

• Indirect

• Direct

• Straightforward

• Alternating

Batteries and cells are sources of...

• Direct current

• Exponential current

• Extrapolated current

• Alternating current

Stars are formed in massive clouds of dust and gas, composed mostly of hydrogen.

What is the name of this type of cloud?

• A supernova

• A protostar

• A black hole

• A nebula

Answer explanation

The massive clouds of dust and gas in which stars are formed are called nebulae.

Gravity pulls the cloud of dust and gas together, causing the cloud to collapse and begin the process of star formation.

A protostar is one of the early stages in the formation of a star.

A supernova is a large explosion at the end of the life of a high-mass star.

Black holes are formed after the supernova explosions of stars with very high masses.

Which statement correctly describes the forces in a main sequence star, like the Sun?

• The force of gravity and the forces due to gas pressure hold the star together

• The force of gravity is balanced by the forces due to gas pressure

• The force of gravity is larger than the forces due to gas pressure

• The force of gravity is smaller than the forces due to gas pressure

Answer explanation

The force of gravity is balanced by the forces due to gas pressure (caused by the high temperatures resulting from nuclear fusion), in a main sequence star like the Sun. 

Because of this, main sequence stars are stable.

Which of these equations correctly shows the main fusion process occurring in the Sun?

• A

• B

• C

• D

In general, the further away a galaxy is, the more red-shifted its light is.

What does this tell astronomers?

• The further away galaxies are, the slower they are moving

• The further away galaxies are, the smaller they are

• The further away galaxies are, the larger they are

• The further away galaxies are, the faster they are moving

Answer explanation

The further away galaxies are, the faster they are moving – as shown by the graph.

This is similar to an explosion, where the bits moving fastest travel furthest from the explosion.

Red-shift data provides evidence that the Universe, including space itself, is expanding.

Next

Which term has the following definition?

"A transformer where the secondary coil has more turns than primary coil."

• Step-up transformer

• Step-down transformer

• Step-straight transformer

• Direct transformer