A Level Physics Practice Exam

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Study for the A Level Physics Exam. Our quiz features flashcards and multiple choice questions, each with hints and explanations. Prepare thoroughly!

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What is the quark substructure of a neutron?

u u d
u d d
d d d
u u u

The correct answer is: u d d

The quark substructure of a neutron consists of one up quark and two down quarks, which is represented as "u d d". This arrangement accounts for the neutron's overall charge of zero, since the up quark has a charge of +2/3 and each down quark has a charge of -1/3. When you sum the charges, the total becomes: (+2/3) + (-1/3) + (-1/3) = 0. This explains why the neutron is electrically neutral, which is one of its defining characteristics in atomic structure. Other combinations do not reflect the correct balance of charges needed to maintain the neutron's neutrality, hence they do not describe the neutron accurately.