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A capacitor discharge circuit of time constant 45ms includes a capacitor and resistor. The capacitor has a capacitance of 18µF What is the resistance of the resistor?

This question is in one of the CIE Physics Pre-U sample papers, and if you know the definition of the time constant for a capacitor circuit (=RC), its very easy, however even if you didnt it canbe derived fa...
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Answered by Sam C. • Physics tutor
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Explain the different types of wave.

There are two different types of wave: longitudinal and transverse . When you hear the word "wave" you are probably thinking of a transverse wave. Imagine you are floating in the sea. The waves of ...
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Answered by Harry C. • Physics tutor
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A pendulum has a frequency of 0.80 Hz, calculate the periodic time of the pendulum.

You need to use the equation that relates frequency and period; period = 1/frequency Then all you need to do is plug in the frequency to get the periodic time: period = 1/0.80 Hz = 1.25 s [NOTE: If you're co...
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Answered by Mia V. • Physics tutor
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What determines the acoustic impedance of a material and why is it useful in understanding ultrasound imaging?

Acoustic impedance is the density of a material multiplied by the speed of sound in the material. Knowing these two values allows use to calculate how much of the sound energy is reflected at an interface be...
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Answered by David A. • Physics tutor
10536 Views

How is a piezoelectric crystal used to generate waves of ultrasound?

A piezoelectric crystal makes use of the peizoelectric effect . This is the production of a voltage when mechanical stress is applied across the material. This occurs only in materials when the unit cells wh...
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Answered by David A. • Physics tutor
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