```4. Shunt : It is a device which allows electric           Kilowatt Hour (kWh)
current to pass around another point in the
circuit by creating a low resistance path.            It is a derived unit of energy equal to 3.6
mega-joules. If the energy is being transmitted
Electrical Conductivity                                   or used at a constant rate (power) over a period
of time, the total energy in kilowatt-hours is
Electrical conductivity, a measure of a                   the product of the power in kilowatts and the
material"s ability to conduct an electric current.        time in hours.
1. Conductors allow electric current to flow              Electric Fuse
with little resistance. Ex: Gold ,silver,
copper, mercury, etc.                                     It is used to protect circuits from over
2. Superconductors allow current to flow                       current, overload and make sure the
with no resistance. Ex: Sn (Tin), Hg                       protection of the circuit.
(Mercury), Pb (Lead), Al (Aluminum),                      All electric appliances like bulbs, fans etc.
etc.                                                       are connected in parallel across the live
3. Semiconductors allow some electric                          wires and the neutral wires
current to flow but with significant                      Fuse consists of a low resistance metallic
resistance. Ex: Silicon, Germanium,                        wire enclosed in a non-combustible
aluminum phosphide, etc.                                   material.
4. Insulators do not allow electric current to
flow. Ex: Wood, Glass, Plastic, Rubber,               Electric Cell
Plants, Diamond, Silicon, Paper, etc.
Electrical cell is a device which converts
Electric Power                                            chemical energy into electrical energy.
   Electric power is the rate of energy                  Electrical Cells are basically of two
consumption in an electrical circuit.
1. Primary Cell : In this cell electrical
   Its unit of power is the watt, one joule per
energy is obtained from the irreversible
second.
chemical reaction taking place inside the
QV                           cell. After completing discharge, primary
P  work done per unit time =     IV
t                           cell becomes unserviceable. Examples
Voltaic cell, Leclanche Cell, Daniel Cell,
   Where, Q is electric charge in coulombs, t                 Dry Cell etc.
is time in seconds, I is electric current in          2. Secondary cells : It can be charged again
amperes, V is electric potential or voltage                and again. Acid and alkali accumulators
in volts.                                                  are the types of secondary cells.
MAGNETIC FIELD
   A magnetic field is the magnetic effect of electric currents and magnetic materials.
   The magnetic field at any given point is specified by both a direction and a magnitude (or
strength); as such it is a vector field.
   The SI unit for magnetic field is the Tesla. A smaller magnetic field unit is the Gauss (1 Tesla =
10,000 Gauss).
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