- 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.
Definitions [15]
Definition: Mass Number
The mass number of an atom is equal to the total number of nucleons (i.e., the sum of the number of protons and the number of neutrons) in its nucleus.
Define the term atomic number.
The number of protons in the nucleus is known as the atomic number of the element and is denoted by Z.
The number of protons in the nucleus of an atom, which is characteristic of a chemical element and determines its place in the periodic table. Atomic number is also equal to the number of electrons in an atom.
Define the term mass number.
The total number of neutrons and protons in the nucleus is called the mass number of the element and is denoted by A.
Definition: Atomic Number
The atomic number of an atom is equal to the number of protons in its nucleus (which is same as the number of electrons in a neutral atom).
Definition: Point Charge
An electric charge which can be considered to exist at a single point is called a point charge.
Definition: Electric Charge
The basic property of matter due to which it experiences electric force and shows attraction or repulsion, is called electric charge.
OR
The fundamental property of subatomic particles that gives rise to the phenomenon of experiencing force in the presence of electric and magnetic fields is called electric charge.
- Positive charge: Deficiency of electrons
- Negative charge: Excess of electrons
- SI unit: Coulomb (C)
- Dimension: [M0L0T1A1]
Definition: Test Charge
A unit positive charge used to test the strength of electric fields is called a test charge.
Define the following:
Electric force
The force existing between the charges is called an ‘electric force’.
Define the term current.
An electric current is a flow of electric charge. In electric circuits this charge is often carried by moving electrons in a wire.
Define the term potential difference.
The amount of work done in moving a unit positive charge from one point to another point in an electric field is called the potential difference.
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 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:
Electrolyte
The solution through which the electricity passes is called an electrolyte.
Define fuse.
Electric fuse is a safety device which is used in household wiring and in many appliances.
Definition: Heating effect of electric current
When a resistor is connected in an electrical circuit, heat is produced in it due to the current. This is known as the heating effect of current.
Formulae [1]
Write the mathematical expression for Joule’s law of heating.
The mathematical expression of Joule’s Law of heating is: H = I2 Rt
Where,
H = Produced Heat
I = Current flowing through the device
t = Time taken
r = Resistance of the appliance
Theorems and Laws [1]
State Ohm’s law.
At constant temperature, the current flowing through a conductor is directly proportional to the potential difference across its ends.
In formula form: V = IR
Where:
- V = Voltage (potential difference)
- I = Current
- R = Resistance
Key Points
Key Points: Structure of the Atom and Nucleus
- The structure of an atom and its nucleus was developed from the discovery of electrons by J.J. Thomson and alpha particle scattering experiments by Rutherford.
- An atom consists of electrons, protons, and neutrons, with protons and neutrons in the nucleus and electrons revolving in stationary orbits.
- The maximum number of electrons in a shell is given by 2n², and the shells are named K, L, M, N, O, P, and Q.
Additivity of Charge
- Electric charge is additive — the total charge of a system is the algebraic sum of all charges in it.
- Example: A system with +5 C and −2 C has a net charge of +3 C.
- Electrostatic forces between two point charges obey Newton's Third Law — action and reaction are equal and opposite.
Key Points: Electric Circuit
Key Points: Heating Effect of Electric Current
- Heating Effect: Current through a resistor produces heat, calculated by H = I²Rt or H = VIt (Joule’s Law).
- Heat Applications: Used in devices like irons, heaters, bulbs, and fuses (to stop excess current).
- Power Unit: 1 kWh = 3.6 × 10⁶ J, called 1 unit of electrical energy in electricity bills.
- Short Circuit & Fuse: A short circuit causes a large current; the fuse wire melts to break the circuit and prevent fire.
- MCBs: Miniature Circuit Breakers automatically cut off power during overload or fault conditions.
Concepts [16]
- Electricity
- Structure of the Atom and Nucleus
- Electric Charge
- Electric Force
- Transfer of Charges
- Direction of the Electric Current - Conventional and Electronic Flow
- Flow of Charges (Electrons) Between Conductor
- Electroscope
- Lightning and Lightning Safety
- Electric Circuit
- Types of Circuits: Simple Circuit
- Types of Circuits: Series Circuit
- Types of Circuits: Parallel Circuit
- Effects of Electric Current
- Heating Effect of Electric Current
- Chemical Effects of Electric Current
