- Electric potential is a scalar quantity, and it is positive near a positive charge and negative near a negative charge.
- Electric potential is taken as zero at infinity because the force between charges becomes zero at infinite separation.
- The potential difference between two points is measured using a voltmeter, which is connected in parallel with the circuit, with its positive terminal at the higher-potential point.
Definitions [33]
Define: An Atom:
An Atom: Smallest particle of an element that can exist and have properties of an element.
Define: Relative atomic mass
Relative atomic mass— Relative atomic mass is the mass of an atom of an element as a multiple of the standard atomic mass unit.
The relative atomic mass of an element is the ratio between the average mass of its isotopes to 1/12th part of the mass of a carbon – 12 atoms. It is denoted as Ar.
Relative atomic mass = `" Average mass of the isotopes of the element"/(1"/"12^{"th"}" of the mass of one Carbon- 12 atom")`
Define the following term with an example.
Compound
Compound: A compound is a pure substance that is formed when the atoms of two or more elements combine chemically in definite proportions.
Ex: H20, NaCl.
Define the following term with an example.
Non-metal
Non-Metal: Non-metal is an element that doesn’t have the characteristics of metal including, (i.e.) ability to conduct heat or electricity luster or flexibility.
Ex. Carbon Iodine, Sulphur.
Define: Mass number
Mass number— Mass number is the sum of the number of protons and neutrons present in the nucleus of an atom. It is denoted by A.
Define: Ions
An atom which becomes charged by losing or gaining electrons is called an ion.
Define:- Atom
Atom: An atom is the smallest indivisible unit of an
OR
Atom is the smallest unit of matter.
Define: Covalent bond
Covalent bond— When atoms of different non-metals neither donate nor accept electrons and hence no ions are formed, such a bond is called covalent bond.
Define:- Molecule
Molecule : Molecule is the smallest unit of a compound (or an element) which always has an independent existance.
Define the following term with an example.
Metal
Metal: A chemical element that is an effective conductor of electricity and heat can be defined as a metal.
Ex.: Copper, Iron, Silver, etc.
Define the following term with an example.
Metalloid
Metalloid: Metalloid is a chemical element that exhibits some properties of metals and some of non-metals. Metalloids are generally semi-conductors.
Ex.: Silicon. Arsenic, Antimony and Boron.
Define – Atom.
An atom is the smallest particle of a chemical element that retains its chemical properties.
Define: Chemical bond
Chemical bond— A chemical bond is the binding force between two or more atoms of a molecule.
Define the following term with an example.
Element
Element: It is a substance that cannot be broken down into simpler substance by chemical means
Ex.: Oxygen, Hydrogen, Gold & Helium.
Define the following term:
Atom
An atom is the smallest particle of an element which retains its chemical identity in all physical and chemical changes.
Define:- Radicals
Radicals : A radical is an atom of an element or a group of atoms of different elements that behaves as a single unit with a positive or negative charge on it.
Define the following:
Super conductors
Substances whose resistance decreases tremendously with decreasing temperature and reaches nearly zero near absolute zero are called superconductors; e.g., lead, tin, etc.
Define the following:
Semiconductors
Semiconductors: Substances whose resistance decreases with the increase in temperature are named as semiconductors. E.g. manganin, constantan etc.
Define an electric current.
An electric current is measured by the amount of electric charge moving per unit time at any point in the circuit.
The magnitude of an electric current is the number of electric charges flowing through a conductor in one second.
Define the following:
Electromotive force
Electromotive force: When no current is drawn from a cell, when the cell is in open circuit, the potential difference between the terminals of the cell is called its electromotive force (or e.m.f.).
Define the following:
Conventional current
The movement of the positive charge is called conventional current.
Define the unit of current.
The unit of electric current is ampere (A). When one coulomb charge flows through an electric circuit in one second, then the electric current flowing through the circuit is said to be an ampere.
Define the term resistivity.
The resistivity of a material is the resistance of a wire of that material of unit length and unit area of cross-section.
Definition: Electric Circuit
A continuous and closed path of an electric current is called an electric circuit.
Definition: Current
Current is defined as the rate of flow of charge.
Define Electric potential.
Electric potential is a measure of work done on the unit's positive charge to bring it to that point against all electrical forces. It is represented as ‘V’.
Definition: Potential Difference
The potential difference (p.d.) between two points is equal to the work done per unit charge in moving a positive test charge from one point to the other.
OR
The work done per unit positive charge in moving a charge from one point to another in an electric field, is called potential difference between those two points.
Define the following:
Potential difference
Potential difference: The potential difference between two points may be defined as the work done in moving a unit positive charge from one point to the other.
Definition: Potential at a Point
The potential at a point is defined as the amount of work done per unit charge in bringing a positive test charge from infinity to that point.
Define the following:
Synaptic signals
Synaptic signals: Extremely weak electric current is produced in the human body by the movement of charged particles. These are called synaptic signals. These signals are produced by the electrochemical process. They travel between the brain and the organs through the nervous system.
Define the following:
Magnetic effect of current
Magnetic effect of current: A wire or a conductor carrying current develops a magnetic field perpendicular to the direction of the flow of current. This is called the magnetic effect of current.
Define the magnetic effect of electric current.
A current-carrying conductor is always associated with a magnetic field around it is called the magnetic effect of current. It was first discovered by Hans Christian Oersted in 1820.
Definition: Electromagnet
An electromagnet is a temporary strong magnet made by passing current in a coil wound around a piece of soft iron. It is an artificial magnet.
Formulae [1]
Formula: Electric Potential at a Point
V = \[\frac {W}{Q}\]
or
W = QV
Key Points
Key Points: Electric Current
- Electricity is a convenient and controllable form of energy widely used in homes, industries, schools, and hospitals.
- Electric current is produced when electric charges flow through a conductor, and it flows only through a closed, continuous electric circuit.
- A switch completes or breaks the circuit; when the circuit is broken, current stops flowing, and devices like bulbs do not glow.
- Electric current is the rate of flow of charge, given by the relation I = Q / t, where Q is charge and t is time.
- In metallic wires, electrons are the charge carriers, but by convention, current flows from the positive to the negative terminal, in the opposite direction to electron flow.
Key points: Potential and Potential Difference
Key Points: Electric Circuit
- Electric energy from a cell is used to do work on charges, which is converted into heat in a resistor or other forms, like motion in a motor.
- The work done (energy) in moving a charge Q across a potential difference VAB is:
Work = VAB × Q - Heat produced (H) in a resistor over time t is given by Joule’s Law of Heating:
H = I2 × R × t - According to Ohm’s Law:
VAB = I × R - Electrical power (P) is the rate of energy transfer and is calculated as:
P = VAB × I
Its unit is watt (W), where 1W = 1 volt × 1 ampere.
Key Points: Magnetic Effect of Electric Current
- Electric current creates a magnetic field, shown by compass needle deflection.
- Oersted discovered the link between electricity and magnetism in 1820.
- Reversing current changes the direction of the magnetic field.
- Iron filings form circular patterns, showing magnetic field lines around the wire.
- Magnetic field strength increases with current and decreases with distance.
