summary of physics chapter 7 something about electricity
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Answer:
Electricity: Electric current, electric circuit, voltage or electric potential, resistance and (Ohm’s law).
Electric Current: The flow of electric charge is known as Electric Current, Electric current is carried by moving electrons through a conductor.
By convention, electric current flows in the opposite direction to the movement of electrons.
Electric Circuit: Electric circuit is a continuous and closed path of electric current.
Expression of Electric Current: Electric current is denoted by the letter ‘I’. Electric current is expressed by the rate of flow of electric charges. Rate of flow means, the amount of charge flowing through a particular area in unit time..
S.I. Unit of Electric Charge and Current: S.I. unit of electric charge is coulomb (C).
One coulomb is nearly equal to 6 × 1018 electrons. S.I. unit of electric current is ampere (A). Ampere is the flow of electric charge through a surface at the rate of one coulomb per second. This means, if 1 coulomb of electric charge flows through a cross section for 1 second, it would be equal to 1 ampere.
Therefore, 1 A = 1 C/1 s
Small Quantity of Electric Current: Small quantity of electric current is expressed in milliampere and microampere. Milliampere is written as mA and microampere as pA.
1 mA (milliampere) = 10-3 A
1 pA (microampere) = 10-6 A.
Ammeter: An apparatus to measure electric current in a circuit.,
Charge: Like mass, the charge is the fundamental property of matter. There are two types of charge
(i) Positive charge.
(ii) Negative charge.
Positive and Negative Charge: The charge acquired by a glass rod when rubbed with silk is called a positive charge and the charge acquired by an ebonite rod when rubbed with wool is called negative charge.
Properties of Electric Charge:
(i) Unlike charges attract each other and like charges repel each other.
(ii) The.force between two charges varies directly as the product of two charges and inversely as the square of the distance (r) between both charges (q1 and q2).
Electricity Class 10 Notes Science Chapter 12 3
S.I. unit of charge is coulomb (C).
1 coulomb = 1 ampere × 1 second.
1C = 1A × 1s
Thus, the quantity of charge which flows through a circuit when one ampere of current flows through it in one second is known as a 1-coulomb charge.
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Electric Potential and Potential Difference
Electric Potential: The amount of electric potential energy at a point is called electric potential.
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 amount of work done to move the unit charge between two points against static electric field.
Therefore, Voltage = WorkdoneCharge
Voltage or electric potential difference is denoted by V’. Therefore, V = WQ
Where, W = Work done and Q = Charge
S.I. Unit of Electric Potential Difference (Voltage)
S.I. unit of electric potential difference is volt and denoted by ‘V’ This is named in honour of Italian Physicist Alessandro Volta.
Since joule is the unit of work and Coulomb is the unit of charge, 1 volt of electric potential difference is equal to the 1 joule of work to be done to move a charge of 1 coulomb from one point to another in an electric circuit. Therefore
1V = 1Joule/1Coulomb = 1J/1C
1V = 1JC-1
Voltmeter: An apparatus to measure the potential difference or electric potential difference between two points in an electric circuit.
Galvanometer: It is a device to detect current in an electric circuit.
Ohm’s Law: Ohm’s Law states that the potential difference between two points is directly proportional to the electric current, at a constant temperature.
This means potential difference V varies as electric current.
V ∝ I
V = RI
I = VR
R = VI
Where, R is constant for the given conductor at a given temperature and is called resistance.
Resistance: Resistance is the property of conductor which resists the flow of electric current through it.
S.I. unit of resistance is ohm. Ohm is denoted by Greek letter ‘Q’
1 Ohm: 1 ohm (Q) of resistance (R) is equal to the flow 1A of current through a conductor between two points having a potential difference equal to 1V.
This means; 1Ω = 1V1A
From the expression of Ohm’s Law, it is obvious that electric current through a resistor is inversely proportional to resistance. This means electric current will decrease with an increase in resistance and vice versa. The graph of V (potential difference) versus I (electric current) is always a straight line.
Electricity Class 10 Notes Science Chapter 12 4
Graph of Potential Difference (V) Vs Electric Current (I)
Voltage, i.e. Potential diffrence (V) = ?
We know, from Ohm’s Law that,
R = VI
15 Ω = V15A
V = 225V
If a net electric charge (Q) flows through a cross-section of a conductor in time t, then,
Electricity Class 10 Notes Science Chapter 12 2
Where I is electric current, Q is a net charge and t is a time in second.
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