Power Formula: P = R l2 = V2/ R = V I
P = E/t: This formula is also called the mechanical power equation. states that the
consumption of energy per unit of time is called power
P = w/t This formula is derived from the work-energy theorem. It states that the work done
per unit time is called power.
P = F × s/t - In this formula, F denotes force applied In the object, s denotes displacement of
the object and t denotes the total time taken.
Electrical power is the rate at which electrical energy is converted to another form, such as
motion, heat, or an electromagnetic field.
DC power - It is defined as the product of voltage and current and is produced by DC sources
like generators, batteries, fuel cells, etc.
AC power - A flow of charge that exhibits a periodic change in direction is called AC power
Node: Node or junction is a point in the circuit where two or more electrical elements are
connected. This specifies a voltage level with a reference node in a circuit.
Branch: The continuous conducting path between two junctions which contains electrical
element in a circuit is referred as branch.
Loop: In an electrical circuit a loop is an independent closed path in a circuit that follows the
sequence of branches in such a way that it must start and ends with same node and it
shouldn’t touch any other junction or node more than once.
Mesh: In an electrical circuit mesh is a loop that doesn’t contain any other loop in its interior.
1800 invention of voltaic pile (Count Alessandro Volta) - conducted electric current, but lost
power rapidly
1836 creation of Daniell cell (Frederic Daniell) - 1st reliable source of electric current
1859 invention of lead-acid battery (Gaston Plante) - first battery that could be recharged by
passing a reverse current through it, still used in automobiles today
1866 invention of "dry" cell battery (Georges Leclanche) - used to power early telephones
1886 invention of 1st dry cell battery using an electrolytic paste (Carl Gassner) - did not
require maintenance, did not spill, could be used in any orientation, and provided 1.5 volts of
electricity
1896 Eveready Battery Company sold the 1st commercially available dry cell battery in the
U.S.
1898 invention of flashlight (Joshua Lionel Cowen)
1899 invention of 1st alkaline battery made of nickel-cadmium battery (Waldemar Jungner) was rechargeable, except cadmium is toxic
1950s the modern zinc-manganese (IV) oxide batteries were 1st invented by Lewis Urry
1971 nickel-hydrogen batteries uses hydrogen gas and are rechargeable, patented by
Alexandr Illich Kloss and Boris Ioselevich Tsenter
1985 Akira Yoshino built the first lithium-ion battery prototype, it was rechargeable and
more stable than the lithium battery
1989 the 1st consumer grade NiMH cells became commercially available - Nickel metalhydride batteries used a metal alloy in place of cadmium
1991 Sony commercialized the lithium-ion battery
1997 the lithium polymer battery was released, these batteries are flexible and compact, and
have a lower energy-density than normal lithium-ion batteries
2015 the NiMH batteries received an upgrade making them more durable and lighter and
able to reach high electron densities
Kirchhoff’s Voltage Law- states that the algebraic sum of voltages in a closed path is equal
to zero that is the sum of source voltages is equal to the sum of voltage drops in a circuit. If
the current flows from higher potential to lower in an element
 By using these laws, we can find the unknown resistances, voltages and currents
(direction as well as value).
 In the branch method, finding the currents through each branch carried by
applying KCL at every junction and KVL in every loop of a circuit.
 In the loop current method, finding current through each independent loop is
carried by applying KVL for each loop and counting all the currents in any element
of a circuit.
 Used in nodal method of finding voltages and currents.
 These laws can be applied to analyse any circuit regardless of the composition and
structure of it.