or
Subelement B
Electrical Math
Section 15
RC Time Constants-2
What is the time constant of a circuit having two 220-microfarad capacitors and two 1-megohm resistors all in parallel?
• 22 seconds.
• 44 seconds.
• 440 seconds.
220 seconds.

What is the time constant of a circuit having two 220-microfarad capacitors and two 1-megohm resistors all in parallel?

220 seconds.

From imfv!fn20xe93iyimqwrsdcjpnu=.

The Time Constant (T) is calculated as follows:
$T = R C$

Since the components are all in parallel, calculate the total resistance and capacitance separately and then multiply R and C to get the time constant.

Total Resistance: $(1M ∗ 1M) ÷ (1M + 1M) = 500 k$ Total Capacitance: $(220 uF + 220 uF) = 440 uF$ Time Constant: $(500 k) ∗ (440 uF) = 220 s$

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What is the time constant of a circuit having two 100-microfarad capacitors and two 470-kilohm resistors all in series?
• 470 seconds.
47 seconds.
• 4.7 seconds.
• 0.47 seconds.

What is the time constant of a circuit having two 100-microfarad capacitors and two 470-kilo ohm resistors all in series?

47 seconds.

From doughboy_260.:

\begin{align} Time Constant = C Total \times R Total\\ C Total = 1 \div ((1 \div .0001) + (1 \div .0001))\\ =.00005\\ \\ R Total = 470000 + 470000\\ = 940000\\ \\ T = .00005 \times 940000\\ =47 \end{align}

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What is the time constant of a circuit having a 100-microfarad capacitor and a 470-kilohm resistor in series?
• 4700 seconds.
• 470 seconds.
47 seconds.
• 0.47 seconds.

What is the time constant of a circuit having a 100-microfarad capacitor and a 470-kilohm resistor in series?

47 seconds.

Convert microfarad and kilohm to their base units and multiply.

470 kilo ohm = 470000 ohms

$0.000100 farad ∗ 470,000 ohms = 47 seconds$

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What is the time constant of a circuit having a 220-microfarad capacitor and a 1-megohm resistor in parallel?
220 seconds.
• 22 seconds.
• 2.2 seconds.
• 0.22 seconds.

What is the time constant of a circuit having a 220-microfarad capacitor and a 1-megohm resistor in parallel?

220 seconds.

From xrt70r:

RC Time Constant= R ∗ C

(1 x 106) ∗ (220 x 10-6) = 220 seconds

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What is the time constant of a circuit having two 100-microfarad capacitors and two 470-kilohm resistors all in parallel?
• 470 seconds.
47 seconds.
• 4.7 seconds.
• 0.47 seconds.

What is the time constant of a circuit having two 100-microfarad capacitors and two 470-kilohm resistors all in parallel?

47 seconds

From wp2ahg:

Convert from microfarads and kilo ohms to farads and ohms before doing the calculation:

470,000 ohms ∗ 0.000100 farad = 47 seconds

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What is the time constant of a circuit having two 220-microfarad capacitors and two 1-megohm resistors all in series?
220 seconds.
• 55 seconds.
• 110 seconds.
• 440 seconds.

What is the time constant of a circuit having two 220-microfarad capacitors and two 1-megohm resistors all in series?

220 seconds.

From doughboy_260:

The equivalent resistance of two $1 MΩ$ resistors in series is $2 MΩ$.

The equivalent capacitance of two $220 μF$ capacitors in series is $110 μF$.

The time constant is $R \times C = ({110 \times 10^{-6}}) \times (2 \times 10^6) = 220 s$.

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