8) electric Field Flashcards
Electric field
A property of the space surrounding an electric charge. It’s expressed as a force acting on other electrical charged bodies
Characteristics:
- intensity determines the magnitude and direction
- potential determines the energy stored by field
Electric field strength E
The electric field is a vector
Pointing in the direction of the force.
Units is V/m
E = F/q
E AND F ARE VECTORS
Electric potentials
The electric field is conservative.
@_m = A_M infinity / Q
@ is potential
M is point of field
Units is volts
Voltage (u)
Voltage is the potential difference between 2 points on the field.
U_MN = @_M - @_N
The work to move a charge Q from the point M to N is
A_MN=qU_MN
Electric fields in Dielectrics
Polarisation- the displacement of charges particles
The electric fields of the displaced charges don’t cancel each other out
The net electric field is smaller than the external field
Relative permittivity
Ęr= E0/E
External field/internal field
Graphical representation
Field intensity is proportional to the density of the field line
Potential of the field is equipotent
Electric field of single point charge
Field line starts at positive or infinity and end at negative or infinity
Circles with arrows going out and plus in the middle
Electric dipole
A system of 2 opposing charges from a distance L away from each other
P=qL is magnitude
Forces and torque on dipole
Homogeneous the electric field is aligned
In a inhomogeneous electric field it varies
Drawings
Electric field of dipole
Drawing
Electro graphics methods
Electrocardiography
Electromyography
Biopotential is the generation of electric fields by living organisms
Electro graphics method 2
Heart is electric dipole place in conductive material. Biopotential of heart can be measured at the surface of the body
Dipole moment depends on
Magnitude
Direction
Limb leads of Einthoven
Lead is the potential difference between two sites of the skin
I left arm to right arm
II left leg to right arm
III left leg to left arm
