Frequency characterizes by itself cyclic processes of fluctuations or the movement on a circle. It is equal to the number of repetitions of process per unit of time. For its measurement learn the number of fluctuations which happened for some period. Sometimes it is measured in more difficult ways. If the period of repetitions is known, it can just be calculated.
It is required to you
- - stop watch;
- - tester;
- - calculator.
Instruction
1. Watching fluctuations or other repeating movements, count some of their quantity. Measure by a stop watch time for which there were these movements. Full wave is return of a body to a starting point, as well as a whole revolution. For determination of frequency? divide the number of fluctuations of N for the period of t for which they happened, measured in seconds. For example, if the pendulum in 20 seconds did 30 fluctuations, then frequency is equal? =30/20=1,5 1/with (Hertz). If the period of fluctuations (time of one fluctuation) is known find frequency? having divided unit for T (? = 1/T). For example, if the period of fluctuations is 0.2 with, then the frequency of this fluctuation will be equal? =1/0.2=5 Hz.
2. To determine the frequency of alternating current take a tester. Tune it into measurement of frequency the special switch. Connect the device to a chain or a source of alternating current, being careful. On the screen of a tester the current frequency in network will appear. For example, frequency is equal in standard household network to 50 Hz.
3. To measure the frequency of an oscillatory contour, find inductance of its coil and capacity of the condenser which are an oscillatory contour. If they are in advance unknown, connect to them the tester tuned, respectively, into measurement of inductance in Henry and electric capacitances in Farads. Find frequency, using Thomson's formula. For this purpose increase number 2 on?? 3.14 and a root square of the work of inductance of L and electric capacitances of C. Divide number 1 into the turned-out result? =1/(2 ·? • vL•C). Example. The oscillatory contour consists also coils inductance 2 mgn and the condenser electric capacitance 80 mkf. Determine its frequency. Substitute values in a formula? =1/(2•3.14•v2•10^ (-3) • 80 · 10^(-6)) Hz =1/(6.28•4•10^ (-4))=0.04•10^4=400.