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Frequency and Hertz

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Frequency and the hertz

Frequency tells us how often something repeats.

frequency = cycles per second
one cycle positive negative 60 Hz

Symbols

f = frequency
Hz = hertz, the unit of frequency
T = period, the time for one complete cycle

f = 1/T

Another way to think of this

If a pendulum completed two full back-and-forth swings every second, its frequency would be 2 Hz. AC uses the same idea: count complete electrical cycles per second.

Where did the name come from?

The hertz is named for German physicist Heinrich Hertz (1857–1894), whose experiments demonstrated electromagnetic waves predicted by James Clerk Maxwell.

Worked example

If one cycle takes 1/60 second, then:

f = 1 ÷ (1/60) = 60 Hz

Try these yourself

60 hertz means how many cycles each second? one cycle positive negative 60 Hz
The hertz is cycles per second. 60 Hz means 60 complete cycles each second.
If one cycle takes 0.5 second, the frequency is:
f = 1/T = 1/0.5 = 2 Hz.
The symbol usually used for frequency is:
Frequency is commonly represented by f and measured in hertz (Hz).
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