Electricity

Mon, 05/27/2019 - 16:43 - Adarsh

Exam Prep Study Notes (Things to remember) 


Exam Prep Study Notes (Things to remember) 


20.1 Current

  • Electric current I is the rate at which charge flows, given by

    I=ΔQ/Δt,

    where ΔQ is the amount of charge passing through an area in time Δt.

  • The direction of conventional current is taken as the direction in which positive charge moves.
  • The SI unit for current is the ampere (A), where 1 A=1 C/s. 
  • Current is the flow of free charges, such as electrons and ions.
  • Drift velocity vd  is the average speed at which these charges move.
  • Current I s proportional to drift velocity vd , as expressed in the relationship I=nqAvd. .......
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  • analogous to the expressions for DC circuits.


20.6 Electric Hazards and the Human Body

  • The two types of electric hazards are thermal (excessive power) and shock (current through a person).
  • Shock severity is determined by current, path, duration, and AC frequency.


20.7 Nerve Conduction–Electrocardiograms

  • Electric potentials in neurons and other cells are created by ionic concentration differences across semipermeable membranes.
  • Stimuli change the permeability and create action potentials that propagate along neurons.
  • Myelin sheaths speed this process and reduce the needed energy input.
  • This process in the heart can be measured with an electrocardiogram (ECG).


     

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