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Explain why a transformer only works with an alternating current and doesn't with a direct current.

A transformer is designed to step-up or step-down a voltage in a wire to make transferring electricity more efficient. To do this they contain two isolated coiled wires (of varied lengths depending on the tr...
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Answered by Brendan W. • Physics tutor
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Define Newtons law of Gravitation (in words or an equation).

Newtons law of gravitation can be described as: The force experienced by a body proportional to the product of the two masses the interaction is between, the gravitational constant 6.67x10 -11 , and the inve...
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Answered by Brendan W. • Physics tutor
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Derive an expression to show that for satellites in a circular orbit T^2 ∝ r^3 where T is the period of orbit and r is the radius of the orbit.

This question is concerned with balancing forces. First, we must consider what forces are acting on the satellites. What is stopping the satellite from shooting off into space and what is preventing it from ...
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Answered by Charlie M. • Physics tutor
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Describe how emission spectra are formed and how they can be used to identify the elemental composition of a star.

Electrons are bound to a nucleus in quantised energy levels. As they gain and lose energy they transition between this energy levels by emitting photons. Emitted photons have energies equal to the change in ...
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Answered by George P. • Physics tutor
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Explain Newton’s law of Gravitation

Newton’s law of gravitation states that the force of attraction between two objects due to their masses is proportional to the product of the two objects and inversely proportional to the distance between th...
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Answered by Mingyuan S. • Physics tutor
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