Current as function of time in an rl circuit with nonzero current at time zero and no battery is derived. When a capacitor is connected to a circuit with a dc supply two processes occur which are called as charging and discharging. Chapter 11 capacitors charging, discharging, simple. Compare the nature of the voltage versus time graph and current versus time graph while charging and discharging. As a result the capacitor discharges through the resistor. In this atom, we will study how a series rc circuit behaves when connected to a dc voltage source. Current flows into the capacitor and accumulates a charge there. Capacitor charging discharge cc tsai 10 capacitor charging equations voltages and currents in a charging circuit do not change instantaneously these changes over time are exponential changes the voltage across the capacitor as a function of time is the current through the capacitor as a function of time is t rc c e r e i. Circuit for rc chargedischarge measurement where vt is the sensor used to measure the potential difference across the capacitor as a function of. Every node in a circuit has capacitance to ground, like it or not, and its the charging of these capacitances that limits real circuit. Rc and lr time constants charging and discharging circuit schematic diagram illustration of the experiment experiment instructions measuring voltage of your circuit.
In the other circuit, there is no voltage source and the capacitor is initially charged to v0. Charging a rc circuit file exchange matlab central. Closing the switch will allow charge to flow from the battery through the resistor into the capaci tor. Most capacitors have capacitances in the range between picofarads. The conductor with positive charge is at a higher voltage then the conductor with negative charge. Doc charging and discharging of a capacitor lab report. Rc circuits circuits that have both resistors and capacitors. The time constant can be determined by observing either the charging.
Rc circuits california state university, fullerton. The canonical charging and discharging rc circuits consider two di erent circuits containing both a resistor rand a capacitor c. In a is the schematic diagram of a capacitor discharging through a resistor. The topic of this project is charging and discharging of capacitor in rc circuits. As presented in capacitance, the capacitor is an electrical component that stores electric charge, storing energy in. Capacitors are circuit elements that store charge, consisting of two separated conductors usually taken to. Theory and experiment on charging and discharging a capacitor. Complete the prelab assignment at the end of the handout.
To extend the charging process, the resistors were used. An insulator can be glass, ceramic, plastic film, air, paper etc. Charging and discharging of capacitor electronics tutorials. The expressions for the charge on, and hence voltage across, a charging capacitor, and the current through the resistor, are derived in the 8. Assume that the circuit has been sitting with the switch open for a long time and there is no charge on the capacitor. Charging and discharging of capacitor in rc circuits by. Circuit designers must be careful to ensure that the period of the square wave gives sufficient time for the capacitor to fully charge and discharge. The capacitor voltage as a function of time is given by. An rc circuit is a circuit containing resistance and capacitance. The rc circuit 1 university of north carolina 74 part 2. The switching circuit used to discuss charging and discharging a.
Charging and discharging in a simple rc circuit4, a resistor and a capacitor are connected in series with a battery and a switch. The capacitor is an electrical component that houses electric charge. The series rc circuit and the oscilloscope we shall use the oscilloscope to study charging and discharging of a capacitor in a simple rc circuit similar to the one shown in fig. An rc circuit is one containing a resistor r and a capacitor c. Charging and discharging the rc circuit charging initially, a capacitor is in series with a resistor and disconnected from a battery so it is uncharged. Lab 7 rc circuits lab report phy 156 physics ii csi. If you cannot find the software then ask your ta, a certified pc expert. A capacitor is discharging when the capacitor power is negative regardless of the shape of the voltage curve.
The rc circuit department of physics and astronomy. The time dependence of the potential di erence vt for the charging and discharging process is shown in figure 2. I have attached the complete project report for your reference and you can download it for free here. The time period taken for the capacitor to reach this 4t point is known as the transient period.
I hope you will enjoy this animation video of capacitor working, charging and discharging and understand the basic concept of rc circuit. Equations of current and electric charge in this code were obtained by applying kirchhoffs loop rule to a simple rc circuit with a battery. When the switch is first closed, the capacitor starts to discharge as shown. Pdf in this experiment, a capacitor was charged to its full capacitance then discharged through a resistor. Rc circuit is simply a circuit with both a resistor and a capacitor.
Lab06 rc circuit lab 26 charging and discharging the rc. It indicates the response time how fast you can charge up the capacitor of the rc circuit. View lab report lab06 rc circuit from em 8656 at university of central florida. Discharging time constants of an rc circuit by terry bartelt. One circuit also contains a constant voltage source vs.
Charging and discharging of capacitors in rc circuit purpose the goal of this project is to verify that 63% charge is stored in a capacitor in an rc circuit at its time constant and 63% charge remains when capacitor is discharged and hence plot a graph between voltage and time. Build the charging circuit and measure voltage across the capacitor when the switch is closed. Consider the capacitor is discharged initially and the switch is open. Rc time constant rc is known as the rc time constant. V b the battery voltage to be read at the start of charging v oc the initial capacitor voltage to be read at the start of discharging let r 20k. Pdf calculating the time constant of an rc circuit researchgate. Charging a capacitor means the accumulation of charge over the plates of the capacitor, where discharging is a completely opposite process. Rc for the time constant of either a charging or discharging rc circuit. Time dependent current and electric charge of a charging rc circuit are calculated and plotted. Capacitor charging and discharging equation and rc time. Schematics of charging and discharging a capacitor. In subsequent atoms, we will study its ac behavior. Discharging time constants of an rc circuit wisconline oer.
Investigatory project report i aim 6 ii introduction 67 iii materials required 7 8 iv theory 8 10 v procedure. In result, we saw that as capacitor was being charged we saw an increase in the. Consider a series rc circuit with a battery, resistor, and capacitor in series. In this experiment, charging and discharging of the capacitor with different resistors were observed. Rc time constant is the time required to charge the capacitor, through the resistor, by 63. The voltage on a charging and discharging capacitor through a. Lecture 7, slide 2 even if only fractions of a second. In explaining the charge and discharge cycles of an rc series circuit, the time interval from time t 0 time zero, when the switch is first closed to time t 1 time one, when the capacitor reaches full charge or discharge potential will be.
In this laboratory you have observed the charging and discharging behavior of a rc circuit. The insulator acts to increase the capacitors charge capacity. Review of charging and discharging in rc circuits an. The experiment connect the signal generator in series with the resistor and capacitor as shown in figure 5. Conclusion in this experiment charging and discharging of. When the capacitor is connected to a battery current will flow and the charge on the capacitor will increase until the voltage across the capacitor, determined by the relationship cqv, is sufficient to stop current from flowing in the circuit.
V10v before switch closed i0, and charge on capacitor q0. Suppose we have the circuit below, with capacitor c, voltage source v and a toggle switch. Charging and discharging the rc circuit power output. At dc capacitor is an open circuit, like its not there. Circuit for rc charge discharge measurement where vt is the sensor used to measure the potential di erence across the capacitor as a function of time. Circuits with resistors and batteries have timeindependent solutions. If the capacitor is initially uncharged and we want to charge it with a voltage source v s in the rc circuit. Rl circuits in an rc circuit, while charging, q cv and the loop rule mean. Charging and discharging of capacitor in rc circuits. As with all electrical circuits, connect up the components of the circuit first, then introduce the measuring equipment in this case the oscilloscope only afterwards.
Lessons in electric circuits, volume 1, chapter 16. Consider a circuit consisting of resistor r ohms, capacitor c farads, a voltage source v voltage and a. For this, the circuit that we used included the resistor and the capacitor with the power supply. Such a series arrangement is called an rc series circuit. The charge c is measured in units of coulomb c, the voltage vin volts v, and the capacitance c in units of farads f. In this animated object, learners examine how current, voltage and the discharging capacitor of a series rc changes during 5 time constants. Ee 201 rc transient 1 rc transients circuits having capacitors. Charging and discharging by kevin maigting on prezi.
Fig 1 shows a simple rc circuit that employs a dc voltage. The rate of decay of the rc discharging curve is steeper at the beginning because the discharging rate is fastest at the start, but then tapers off exponentially as the capacitor looses charge. Pdf the beauty of a diode lies in its voltagedependent nonlinear resistance. If a switch is added to the circuit but is open, no current. A capacitor can be slowly charged to the necessary voltage and then discharged. We shall use the oscilloscope to study charging and discharging of a capacitor in a simple rc circuit similar to the one shown in. As the charge increases, the voltage rises, and eventually the voltage of the capacitor equals the voltage of the source, and current stops flowing. It can be shown 3 that, as a general rule of thumb, the time necessary for the capacitor of an rc circuit to nearly completely charge to, or discharge to zero, is. After a period equivalent to 4 time constants, 4t the capacitor in this rc charging circuit is virtually fully charged and the voltage across the capacitor is now approx 98% of its maximum value, 0. A charged capacitor can then be discharged by draining the current through its two terminals or connecting some load through its terminals. The expressions for the charge on, and hence voltage across a charging capacitor, and the current through the resistor, are derived in the 8.
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