Identify the basic units of capacitance – Identify different types of capacitors – Determine total capacitance in series and parallel circuits – Explain RC time constants and how they relate to capacitance
Capacitance • Capacitance – Ability to store electrical energy in an electrostatic field – Basic unit is the farad (F) – Represented by letter C • Capacitor – Possesses a specific amount of capacitance – Either fixed or variable
Capacitors • Factors that affect capacitance – Area of the plate – Distance between the plates – Type of dielectric material – Temperature Figure 11-1. A capacitor consists of two plates (conductors) separated by a dielectric (insulator or nonconductor).
Note • Capacitor fully charge act as energy source • Donot touch with bare hands • shorting their leads to discharge the touch • In DC circuits act as an open circuit at initial charge ,as have infinite resistance.
Capacitance (cont’d.) Fig 11-3. Electrolytic capacitors. Fig 11-4. Paper and plastic capacitors.
Capacitors (cont’d.) Fig 11-5. Ceramic disk capacitors. Fig 11-6. Variable capacitors.
Capacitors (cont’d.) • Total capacitance in series circuits: • Total capacitance in parallel circuits:
RC Time Constants Figure 11-7. Circuit used to determine RC time constant. • RC circuit time constant formula: t = RC where: t = time in seconds R = resistance in ohms C = capacitance in farads
Summary • Capacitance ( C ) allows for the storage of energy in an electrostatic field • The unit of capacitance is the farad (F) • Capacitor types include: electrolytic, paper, plastic, ceramic, and variable • Total capacitance in series circuits:
Summary (cont’d.) • Total capacitance in parallel circuits: • RC circuit time constant formula: t = RC • It takes five constants to fully charge and discharge a capacitor
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- Summer '17