Chapter electricity ki sari definition
Answers
Answer:
Electric current: The flow of electric charges across a cross-section of a conductor constitutes an electric current. It is defined as the rate of flow of the electric charge through any section of a conductor. Electric current = charge/Time or I = Q/t Electric current is a scalar quantity.
Insulator: A substance that has infinitely high resistance does not allow electric current to flow through it. It is called an insulator‘. For example rubber, glass, plastic, ebonite etc.
Conductor: A substance which allows passage of electric charges through it easily is called a conductor‘. A conductor offers very low resistance to the flow of current. For example copper,silver, aluminium etc.
Electric circuit: The closed path along which electric current flows is called an electric circuit‘.
Conventional current: Conventionally, the direction of motion of positive charges is taken as the direction of current. The direction of conventional current is opposite to that of the negatively charged electrons.
Potential difference between two points: The Potential difference between two points in an electric field is the amount of work done in bringing a unit positive charge from one to another. Potential difference = Work done/Charge or V = W/Q
Ammeter: It is device to measure current in a circuit. It is always connected in series in a circuit.
Voltmeter: It is a device to measure potential difference. It is always connected in parallel to the component across which the potential difference is to be measured.
Ohm’s law: This law states that the current passing through a conductor is directly proportional to the potential difference cross its ends, provided the physical conditions like temperature, density etc. remains unchanged. V α I or V = RI
Resistance: It is a property of a conductor by virtue of which it opposes the flow of current through it. It is equal to the ratio of the potential difference applied across its ends and the current flowing through it. Resistance = Potential difference/Current or R = V/I
Resistivity: It is defined as the resistance offered by a cube of a material of side 1 m when current flows perpendicular to its opposite faces. Its S.I. unit is ohm-meter (Ωm). Resistivity, ρ = RA/L
Electric energy: It is the total work done in maintaining an electric current in an electric circuit for given time.
Electric energy, W = VIt = I²Rt joule
Electrical power: Electrical power is the rate at which electric energy is consumed by an appliance.
P = W/t = VI = I²R = V²/R