Introduction to SAT II Physics - FreeExamPapers

5. C
The relationship between the voltage in a primary coil and in a secondary coil is given by the formula:
Since the primary has an emf of 5.0 V, and the secondary has twice as many turns as the primary, the
secondary has an emf of 10 V.
Waves
WAVE PHENOMENA OCCUR ALMOST anywhere there is periodic motion. We have
already encountered such periodic motion in the back-and-forth movement of pendulums
and masses on a spring and with the cyclic orbits of objects in a gravitational field. The
physics of waves is also central in explaining how light and sound work. Anything from a
violin string to a drum skin to a wine glass can make a sound, suggesting that there are
few things in the world that cannot produce wave phenomena. We find waves in the air,
in our bodies, in earthquakes, in computers—and, if we’re surfers, at the beach.
Periodic Motion
We’ve already covered some of the basics of periodic motion with our discussion of a
mass on a spring back in Chapter 5. When the end of a spring is stretched or compressed,
the spring exerts a force so as to return the mass at its end to its equilibrium position.
The maximum displacement of the mass from its equilibrium position during each cycle
is the amplitude of the oscillation. One cycle of periodic motion is completed each time
the spring returns to its starting point, and the time it takes to complete one cycle is the
period, T, of oscillation. The frequency, f, of the spring’s motion is the number of
cycles it completes per second. A high frequency means each period is relatively short, so
frequency and period are inversely proportional:
Frequency is measured in units of hertz (Hz), where 1 Hz = 1 cycle/second. The unit of
hertz is technically defined as an inverse second (s –1 ) and can be applied to any process
that measures how frequently a certain event recurs.
We can summarize all of these concepts in an equation describing the position of the
mass at the end of a spring, x, as a function of time, t:
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