9.4 msec

67.

Write an explanation of what is meant by the "RC time constant" of an RC circuit.

or

9400 sec

The time it takes 68.

In addition to one RC time, which represents the time constant of the circuit (a 63%

a capacitor to

change) there are three other constants and percentages relative to all RC circuits which

change its charge

by 63%.

must be remembered. They are:

(1) In .1 RC time, C changes its charge by 10%.

(2) In 2.3 RC time, C changes its charge by 90%.

(3) In 10 RC time, C changes its charge by 100%.

As with 1 RC time and 63% change, these constants and percentages will hold true for

any RC circuit.

EXAMPLE: An RC circuit of 10 ohms and 1 farad has an RC time constant of 10 seconds.

In one tenth (.1) of the RC time, or 1 second, the capacitor changes its charge by

10%.

In 2.3 times the RC time, or 23 seconds, the capacitor changes its charge by 90%.

In 10 times the RC time, or 100 seconds, the capacitor changes its charge by 100%.

The four common values of RC time and the percentage of capacitor voltage change

for each are:

(1) .1 RC time - 10% change.

(2) 1 RC time =

% change.

(3) 2.3 RC time =

% change.

(4) 10 RC time =

% change.

(2) 63

69.

List the percentage of capacitor voltage change for each of the RC times below.

(3) 90

(1) .1

RC time =

% change.

(4) 100

(2)

1

RC time =

% change.

(3) 2.3

RC time =

% change.

(4) 10

RC time =

% change.

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