Cuent Electricity
Electric Current
Direct Current
It is the current flowing in one direction with a
constant magnitude. Electric Current
Source of Electric Current It is the rate of flow of charge across a cross
section normal to the direction of flow of
➡ Cells current.
➡ Batteries
Charge(Q) = n.e
SI unit of charge is coulomb(c)
Cells
Charge of electron = 1.6 x 10-19
➡ Cells:- In a cell chemical energy gets
converted into electrical energy. It has two Current(I) = Q/t = ne/t
conducting roles called as electrodes[anode
and cathode] it is immersed in a solution SI unit of current = Ampere
called as electrolyte.
➡ There are two types of cells:- Current is a scaler quantity.
• Primary cells:- In such kind of cells the
chemical reaction is irreversible, they are 1 Ampere(A) = The flow of current of 1A which
also known as use and throw type of is caused by 1 charge in 1 second.
cells. Ex:- simple voltaic cells, Daniel cells,
dry cells.
1 milli Alphere(1mA) = 10-3 A
• Accumulators:- These kind of cells have
reversible chemical reaction can be used 1 micro Ampere(1μA) = 10-6 A
for larger period of time by using it again
and again. Here the cells is first charged
by D.C source and stores and the
electrical energy is converted into chemical
energy and then stored, which is later
used as electrical energy. There are two
types of accumulators:- Lead and NIFE.
Conductors:- The substances which allow
electric current to flow through them easily
are called conductors. They have a large
number of free electrons.
Insulators:- The substances which don't allow
current to flow through them are called
insulators. They have no free electrons.
Potential Difference and Resistance
Potential:- The work done to move a positive Factors affecting resistance
test charge from infinity to the point where
the force of attraction of a object exist. ➡ The material of wire:- The resistance of
wires of same length, same area of cross
It is a scalar quantity. section but of diff material diff depending
on this material. Good conductors have
V = W/Q higher concentration of free electrons
SI unit:- V, J/C ➡ The length of wire:- If a wire has a long
length then it will have more free electrons
Resistance
which will increase resistance. R ∝ l
The obstruction offered to the flow of current ➡ The area of cross section:- When there is
by a conductor is called its electrical a big area of cross section then the
resistance. resistance decreases. R ∝ 1/a
➡ The temperature of a wire:- When there is
a increase in temperature then the particles
acquire kinetic energy due to which the
resistance increases. R ∝T
Ohm’s Law
It states that current flowing through in a V
conductor is directly proportional to the =R
potential difference applied across its two I
ends if the temperature is constant and
resistance of the wire is the ratio between Resistance is a scalar quantity. SI unit:- V/A
WD and I or Ω
1 ohm:- When 1 volt of potential difference is
across the current of 1A flows through the
wires.
V = IR
Efficient use of energy
➡ The fuel efficiency in the vehicles can be
➡ The use of compact fluorescent lights(CFL) increased by reducing the weight of the
saves 67% energy and they may last 6 to 10 vehicle using the advanced tyres and the
times longer than the incandescent lights. computer controlled engines.
➡ The use of LED bulbs for lighting reduces
the consumption of energy drastically. It is
also helpful in reducing global warming and
the harmful effect of mercury used in the
fluorescent light.
Social Initiatives
➡ The efforts so as to develop the energy
efficient machines.
➡ The technologies which can reduce the
energy expenditure and minimise the
environmental hazards.
