APHY202 9/21/ Capacitance   Ratio of the charge on a conductor to the potential difference between the conductors.   Units of farads (F) Usually in μF or pF ( F)

APHY202 9/21/ Capacitance   For a parallel-plate capacitor:   Applications: cameras, computers, TVs, noise filters, starter motors, etc.

APHY202 9/21/ Dielectrics   An insulating material placed between plates of a capacitor that increases the capacitance: C = κ C o   The polarization of the dielectric will cause an decrease in the electric field. Application: measure humidity in air

APHY202 9/21/ Storage of Electric Energy   Work done to move Δq through V is ΔW= VΔq Total work = ½QV   PE stored = ½QV = ½CV 2 = Q 2 /2C   The energy is stored in the electric field between the plates with a density of ½ ε o E 2. Defibrillators

APHY202 9/21/ Storage of Electric Energy ) Battery Compartment 2) Capacitor 3) Transformer 4) Capacitor 5) Diode 6) Transformer 7) Neon Indicator Light 8) Capacitor 9) Resistor 10) Flash Tube 11) Transistors

APHY202 9/21/ The Electrocardiogram   Cell area ~ 10 5 m 2   Charge per surface ~ C   Depolarization

APHY202 9/21/ The Electrocardiogram

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