Types of electric charge
(i) Positive charge- The charge acquired on a glass rod
when rubbed with silk cloth is called a positive charge.
It is denoted by (+ve) Charge.
ii) Negative charge- The charge acquired on an ebonite rod
when rubbed with woollen cloth is called a negative charge.
It is denoted by (-ve) Charge.
* Opposite or unlike charge attract each other.
* Similar or like charges repel each other.
* Benjamin Franklin gave the name of the two types of charge
positive and negative.
* SI unit of electric charge is Coulomb which is denoted by
“C”.
2) One Coulomb- The quantity of electric charge which
exerts a force of
9 × 109 Newton on an equal charge placed at
a distance of 1 metre is called One Coulomb.
Q) Calculate the number of electrons in 1 C of
Charge?
-> As we know that Charge of Electron is 1.6 × 10-19 C.
So,
thus,
In 1 C of charge, the numbers of electrons are 6.25 × 1018 electrons.
* Free electrons- The conductors have some electrons
which are loosely held by the nuclei of their atoms and these
electrons are called free electrons.
3) Electricity- The physical phenomenon arising from the behaviour of electron and proton that is caused by the attraction of particles with a positive charge and repulsion of
particles with the same charge called electricity.
Electricity are two types:-
(i) Static electricity- When two bodies are rubbed
together, they acquire the property of attracting light objects
like small bits of paper, dust particles etc. this property is
called static electricity.
(ii) Current electricity- The rate of flow of charge per unit
time is called current electricity or electric current. The
direction of current electricity is the direction of flow of
positive charge.
Note:-
* Conductors- Conductors are those materials which allow
electricity to pass through themself.
E.g. metals like silver, iron, copper etc.
-> Earth and moist particles act as a conductor.
* Insulator- Insulators are those materials which do not
allow electricity to pass through themself.
E.g. paper, wood, glass etc.
4) Electric current- The rate of flow of charge per unit
time is called an electric current.
In other words, the quantity of charge flowing per unit
time is called an electric current.
-> The amount of charge from a current of one ampere flowing for
one second is called one coulomb.
Q = It
* SI unit of electric current is ampere and it is a scalar
quantity.
* One Ampere- The rate of flow of one coulomb of charge
flows through any
cross-section of a conductor in one second
is called one ampere.
1 A = 1 C/1 t
* Smaller unit of current is milliampere(mA).
* The very small unit of current is microampere(μA).
-> “Ampere” named after the French mathematician
Andre Marie Ampere (1775-1836).
* Electric current is measured by the ammeter.
An ammeter is an instrument which measures electric current.
It is always connected in series in a circuit.
While connecting the ammeter in a circuit, its positive terminal should be connected to the positive terminal of the
battery and its negative terminal should be connected to the negative terminal of the battery.
Electric circuit
-> Electrons cannot jump freely through the air to the positive terminal of the battery, they need a circuit to move.
When a source of energy like a battery is connected to a light
bulb, the electrons can move from the battery to the light
bulb and vice versa. This arrangement is called an electric
circuit.
In simple words, we can say that continuous and closed
path of an electric current is called an electric circuit.
Electric circuits are two types:-
i> Open circuit- We can stop the current from flowing by
attaching a switch into the circuit. Switch act as a conducting
link between the battery and the bulb. So when the switch is
turned off the current stop flowing and the bulb does not
glow.
Such a circuit is called an open circuit.
ii> Closed circuit- when current flows through a circuit then that circuit is called a closed circuit.
Note:- An electrical load is an electrical component or portion of
a circuit that consumes (active) electric power.
In electric power circuits, examples of loads are appliances
and lights.
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