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A defibrillator shocks a patient’s heart back to the normal rhythm. All of us have witnessed this procedure in popular culture. A person is instructed to give 400 joules to resuscitate a person who is about to die. A capacitor actually houses the energy that the defibrillator delivers to the dying person. SI energy is commonly measured in joules.
Devices like calculators use capacitors to store their energy. These capacitors are then used to provide energy to the device when needed. Flashbulbs on cameras also employ capacitors as a power source. This article covers the meaning of a capacitor, its applications, examples and the steps to calculate the energy stored in a capacitor.
How to Calculate the Energy Stored in a Capacitor?
In a capacitor, Q is charge and V is voltage. They are closely related to the energy it houses. We need to exercise caution when using the equation, ⃤ PE = , ⃤ qV to represent the potential energy. PE is used to symbolise the energy of Q passing through V.
The capacitor usually begins with no voltage and builds it up over time until it reaches its maximum potential. Voltage changes to ⃤ V = 0 for the first time because capacitors have no energy when they are not charged. After being charged to its maximum voltage, ⃤ V=V.
The full charge q experiences an average voltage of V/2, which is the same as the voltage of V/2. As a result of the capacitor’s stored energy, Ecap = QV/2, the charge that is applied on a capacitor that has an applied voltage V is known as Q. The energy will not actually be QV, but instead QV/2.
There are three equivalent formulations for Ecap because charge, as well as voltage, are connected to the capacitance C by the formula:
Ecap = QV/2 = CV2/2 = Q2/2C
In the formula, Q denotes the charge, and V indicates the voltage across a capacitor C, respectively. Joules, coulombs, voltage, and capacitance are measured in volts and farads.
A defibrillator’s ability to rapidly deliver a significant charge to a set of paddles across a person’s chest can save a life. Atrial or ventricular fibrillation may have been the culprit in a heart attack. A severe electrical shock can be used to stop arrhythmias and restore the body’s pacemaker.
Ambulances are now equipped with defibrillators, which use an electrocardiogram to monitor a patient’s heart rate.
AEDs (automated external defibrillators) can be found in almost any public place. They use a proper quantity of energy and waveform to administer the shock after determining the patient’s cardiac status. CPR should almost always precede AED use in many situations.
Example
A heart defibrillator discharges a capacitor at 1.00 x 104 V to deliver 4.00 x 102 J of energy. What will its capacitance be?
The capacitance C is to be determined from the values of Ecap and V. The most convenient of the three in the problem for Ecap is Ecap = CV2/2.
Let us use the figures in the problem in the formulae and figure out the answer:
C = 2Ecap/V2 = 2(4.00×102 J)/(1.00 x 104 V)2 = 8.00 x 10-6 F
= 8.00μF
Applications of a Capacitor
Battery power: Capacitors can store electric energy when linked to a circuit. A temporary battery might still be used even if it were to be unplugged from the power source. When batteries need to be swapped, capacitors help maintain a steady power supply. This minimises data loss in volatile memory.
Power and weaponry in rapid succession: Low inductance and high voltage capabilities make capacitors ideal for a wide range of pulsed power devices that require high current levels. Pulsed lasers, particle accelerators, and electromagnetic devices can all be housed in these gadgets.
Strength training: Capacitors can be used for power conditioning. Full or half-wave rectifiers benefit from their inclusion in power supplies. The higher voltages generated by capacitors help store energy, making them helpful in charging pump circuits.
Safety of Capacitors
Massive amounts of energy can be dangerous if not properly controlled or handled with precaution in the case of capacitors. If a capacitor is disconnected from the power supply for an extended period, the enormous quantity of energy might cause catastrophic electrical shocks and potentially kill the equipment. Capacitors should always be discharged before using any electrical device to avoid this.
Conclusion
Calculators, defibrillators, and flashbulbs all employ capacitors to store energy. There are three methods to express the amount of energy stored:
Ecap = QV/2 = CV2/2 = Q2/2C
Capacitance is represented by C, charge is represented by Q and Voltage by V. The unit of charge is coulombs, capacitance is farads, and the unit of voltage is volts. Now that we are done with the topic of how to calculate the energy stored in a capacitor, let’s look at the question ‘how to calculate the energy stored in a capacitor?’ and its answer.
