Ohm"s Law Electromagnets
It deals with the relationship between An electromagnet is a type of magnet in
voltage and current in an ideal conductor. which the magnetic field is produced by
This relationship states that, the potential an electric current. The magnetic field
difference (voltage) across an ideal disappears when the current is turned off.
conductor is proportional to the current Electromagnets usually consist of a large
through it. number of closely spaced turns of wire
Ohm"s Law is given by: that create the magnetic field.
V = I R , where V is the potential
difference between two points which Electronics
include a resistance R. I is the current It deals with electrical circuits that involve
flowing through the resistance. The active electrical components such as vacuum
constant of proportionality is called the tubes, transistors, diodes and integrated
"resistance", R. circuits, and associated passive
For biological work, it is often preferable interconnection technologies.
to use the conductance, g = 1/R ; in this
form Ohm"s Law is: I = g V Electrical resistance and conductance
Electric Field Conductance (G) is a measure of how
well an artefact (such as an electrical
Electric field is defined as the electric component, not a material, such as iron)
force per unit charge (E = F/q) carries an electric current. It is measured
The direction of the field is taken to be the in Siemens (S).
direction of the force it would exert on a Resistance (R) is a measure of how well
positive test charge. an artefact resists an electric current. It is
The electric field is radially outward from measured in Ohms (Ω).
a positive charge and radially in toward a The resistance (R) of an object is defined
negative point charge. as the ratio of voltage across it (V) to
Electric field intensity inside a charged current through it (I), while the
hollow conductor, hollow conductor & conductance (G) is the inverse:
spherical surface is zero.
V I 1
R , G , G
Electric Potential I V R
It is the capacity of an electric field to do 1 S = 1 ohm -1
work on an electric charge, typically
measured in volts. Measuring instrument
It is the "push" of electricity through a 1. Ammeter : It is a measuring instrument
circuit. used to measure the electric current in a
The electric potential at infinity is circuit.
assumed to be zero. 2. Voltmeter : It is an instrument used for
Force and potential energy are directly measuring electrical potential difference
related. between two points in an electric circuit.
3. Galvanometer : It is an instrument used
to indicate the presence, direction, or
strength of a small electric current.