**measure that helps us figure out how long it will take a cap to charge to a certain voltage level**. The RC constant will also have some handy uses in filtering that we’ll see later on. Calculating the RC is straight forward — multiply the capacitance C, in Farads, by the resistance R, in Ohms.

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The RC circuit is used in camera flashes, pacemaker, timing circuit etc. The RC signal **filters the signals by blocking some frequencies and allowing others to pass through it**. It is also called first-order RC circuit and is used to filter the signals bypassing some frequencies and blocking others.

The resistive-capacitive (RC) time constant is **the time required to charge a capacitor to 63.2 percent of its maximum voltage.**

RL Circuit Uses Used as **high pass filter** or low pass filter. Used in chokes of tube lights. Used in the filtering of low power signals and stores energy in the form of potential magnetic energy.

RC Circuits. An RC circuit is a circuit with **both a resistor (R) and a capacitor (C)**. … A capacitor can store energy and a resistor placed in series with it will control the rate at which it charges or discharges. This produces a characteristic time dependence that turns out to be exponential.

The time constant, τ is found using the formula **T = R*C in seconds**. a) What value will be the voltage across the capacitor at 0.7 time constants?

Why do we need to make the RC time constant at least five times the half period of the input signal greater? … **To keep a constant voltage on the capacitor over the period of the input, the RC time constant must be large.**

Time constant means **how fast the system reaches the final value**. As smaller the time constant, as faster is the system response. If time constant is larger, system goes to move slow.

These three components together in different combinations will form the RC, RL and RLC circuits and they have many applications like from **filtering circuits, Tube light chokes, multivibrators etc**..

The **combination of a resistor and capacitor connected in series to an AC source** is called a series RC circuit. Figure 1 shows a resistor and pure or ideal capacitor connected in series with an AC voltage source. The current flow in the circuit causes voltage drops to be produced across the capacitor and the resistor.

The time required for the current flowing in the LR series circuit to reach its maximum steady state value is equivalent to about 5 time constants or 5τ. This time constant τ, is measured by **τ = L/R, in seconds**, where R is the value of the resistor in ohms and L is the value of the inductor in Henries.

As with the purely capacitive circuit, **the current wave** is leading the voltage wave (of the source), although this time the difference is 79.325° instead of a full 90°. Voltage lags current (current leads voltage)in a series R-C circuit.

The time constant for the circuit, τ, is the time for the voltage (or current, or charge) to decay to 1/e (≈ 0.368) of its initial value. It is a measure of the response time for the circuit. Hence a graph of ln V vs. t will yield a straight line with slope equal to **–1/RC = –1/τ**, as illustrated in Figure 3.

A fully charged capacitor discharges to **63% of its voltage after one time period**. After 5 time periods, a capacitor discharges up to near 0% of all the voltage that it once had. Therefore, it is safe to say that the time it takes for a capacitor to discharge is 5 time constants.

The time constant of charge and discharge of the capacitor determines **the output of** a clamper circuit. In a clamper circuit, a vertical shift of upward or downward takes place in the output waveform with respect to the input signal.

At the RL circuit, at time = L/R sec, the current becomes 63.3% of its final steady-state value. The L/R is known as the time constant of an LR circuit. … The time constant of an LR circuit is **the ratio of inductance to the resistance of the circuit**. Let us take another.

The major difference between RC and RL circuits is that **the RC circuit stores energy in the form of the electric field while the RL circuit stores energy in the form of magnetic field**.

• Transient – **a circuit changes from one DC configuration to another**. **DC configuration** (a source value changes or a switch flips). Determine the DC state (current, voltages, etc.) before the change. Then determine what happens after the change.

A capacitor **blocks DC** as once it gets charged up to the input voltage with the same polarity then no further transfer of electrons can happen accept to replenish the slow discharge due to leakage if any. hence the flow of electrons which represents electric current is stopped.

The natural response tells us **what the circuit does as its internal stored energy (the initial voltage on the capacitor) is allowed to dissipate**. It does this by ignoring the forcing input (the voltage step caused by the switch closing). The “destination” of the natural response is always zero voltage and zero current.

If capacitor value is small, one may get a severe shock, but it does not have enough punch to kill. **You can definitely die from getting electrocuted by high voltage charged capacitors**. Even the high voltage cables, once disconnected from power, can retain a lethal amount of charge.

- At 0.7 time constants ( 0.7T ) Vc = 0.5Vs. Therefore, Vc = 0.5 x 5V = 2.5V. …
- At 1 time constant ( 1T ) Vc = 0.63Vs. Therefore, Vc = 0.63 x 5V = 3.15V. …
- 1 time constant ( 1T ) = 47 seconds, (from above). Therefore, 5T = 5 x 47 = 235 secs.

The basic formula governing capacitors is: **charge = capacitance x voltage**. **or**. **Q = C x V**. We measure capacitance in farads, which is the capacitance that stores one coulomb (defined as the amount of charge transported by one ampere in one second) of charge per one volt.