Electric Current:
The flow of electric charge is known as electric current.
Electric current is carried by
moving electrons through a conductor.
Electric current flows in the
opposite direction of the movement of electrons.
Electric circuit:
Electric circuit is a continuous and closed path of electric current.
Electric current is denoted by
letter ‘I’.
Electric current
is expressed by the rate of flow of electric charges, i.e. amount of charge
flowing through a particular area in unit time.
SI unit of electric charge is
coulomb (C). One coulomb is nearly equal to 6 x 1018 electrons.
SI unit of electric current is
ampere (A). Ampere is the flow of
electric charges through a surface at the rate of one coulomb per second. 1mA
(milliampere)= 10-3 A AND 1μA(microampere)=10-6 A
Ammeter: An apparatus
to measure electric current in a circuit.
Electric Potential:
The amount of electric potential energy at a point is called electric
potential.
Electric Potential difference: The difference in the amount of electric potential energy
between two points in an electric circuit is called electric potential
difference.
Electric potential difference is known as voltage, which is equal to the work done per
unit charge to move the charge between two points against static electric
field. It is denoted by ‘V’.
Voltmeter:
An apparatus to measure the potential difference or electric potential
difference between two points in an electric circuit.
Ohm’s Law:
The potential difference between two points is directly proportional to the
electric current.
SI Unit of resistance is ohm. Ohm is
denoted by Greek letter ‘Ω’.
1 ohm (Ω) of Resistance (R) is equal to the flow of 1 A of
current through a conductor between two points having potential difference
equal to 1 V.
Component that is used to resist the
flow of electric current in a circuit is called resistor.
Variable Resistance:
The component of an electric circuit which is used to regulate the current;
without changing the voltage from the source; is called variable resistance.
Rheostat: This is a
device which is used in a circuit to provide variable resistance.
Resistance in a conductor depends on
nature, length and area of cross section of the conductor.
Resistance increases with increase
in length of the conductor. Resistance decreases with increase in thickness of
conductor.
Resistors in Series:
When resistors are joined from end to end, it is called in series. The total
resistance of the system is equal to the sum of the resistance of all the
resistors connected in series in the system.
Resistors in parallel:
When resistors are joined in parallel, the reciprocal of total resistance of
the system is equal to the sum of reciprocal of the resistance of resistors.
When electric current is supplied to
a purely resistive conductor, the energy of electric current is dissipated
entirely in the form of heat and as a result, resistor gets heated. The heating
of resistor because of dissipation of electrical energy is commonly known as
Heating Effect of Electric Current.
Joule’s Law of Heating:
Heat produced in a resistor is directly proportional to the square of current
given to the resistor, directly proportional to the resistance for a given
current and directly proportional to the time for which the current is flowing
through the resistor.
SI unit of electric power is watt
(W).
1W = 1 volt x 1 ampere = 1V x 1A
1 kilo watt or 1kW = 1000 W
1 kWh = 1000 watt x 1 hour = 1000 W x 3600 s ⇒ 1kWh = 3.6 x 106 watt
second = 3.6 x 106 J.
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