Static Electricity
Static electricity is the buildup of electric charge on the surface of objects.
1. Basic Concepts:
○ Atoms: Made up of protons (positive charge), neutrons (neutral), and electrons
(negative charge).
○ Charging by Friction: When two objects are rubbed together, electrons are
transferred from one to the other. One object becomes positively charged (loses
electrons), and the other becomes negatively charged (gains electrons).
○ Like Charges Repel, Opposite Charges Attract: Objects with the same charge
repel each other, while objects with opposite charges attract.
2. Electric Fields:
○ Electric Field: A region around a charged object where another charged object
will experience a force.
○ Field Lines: Lines that show the direction of the electric field. They point away
from positive charges and towards negative charges.
3. Examples of Static Electricity:
○ Rubbing a balloon on your hair to make your hair stand up.
○ Lightning, where static charge builds up in clouds and discharges to the ground.
Magnetism
Magnetism is the force exerted by magnets on other materials, and it is closely related to
electricity.
1. Magnetic Poles:
○ Poles: Every magnet has two poles: a north pole and a south pole.
○ Like Poles Repel, Opposite Poles Attract: If you bring the same poles of two
magnets together, they will repel; opposite poles attract.
2. Magnetic Fields:
○ Magnetic Field: A region where magnetic forces can be felt. It is represented by
magnetic field lines that run from the north pole to the south pole.
○ Earth's Magnetic Field: The Earth acts like a giant magnet with a magnetic
north and south pole.
3. Electromagnets:
○ Electromagnet: A magnet created by passing current through a coil of wire. The
strength of the magnetic field can be increased by increasing the number of coils
or the current.
4. Applications of Magnetism:
○ Magnets are used in compasses, electric motors, and magnetic storage devices.
Circuits
A circuit is a closed loop that allows electric current to flow.
1. Components of a Circuit:
○ Power Source: Provides the energy (e.g., a battery).
○ Conductors: Wires that carry electric current.
○ Load: A component (like a light bulb) that uses electricity.
○ Switch: A device used to open or close the circuit.
2. Types of Circuits:
○ Series Circuit: All components are connected end-to-end. If one component
fails, the entire circuit is broken.
○ Parallel Circuit: Components are connected in separate branches. If one
component fails, the others continue to work.
3. Ohm’s Law:
○ Ohm's Law: The relationship between voltage (V), current (I), and resistance (R)
is given by the formula: V=I×RV = I \times RV=I×R
○ Voltage (V): The potential difference between two points in a circuit.
○ Current (I): The flow of electric charge.
○ Resistance (R): The opposition to the flow of current.
4. Power in Circuits:
○ Power (P) is the rate at which energy is used or transferred. It is calculated using
the formula: P=V×IP = V \times IP=V×I
○ Power is measured in watts (W).
Electromagnetism
Electromagnetism is the interaction between electric fields and magnetic fields.
1. Magnetic Fields and Current:
○ A current-carrying wire generates a magnetic field around it. The strength of the
magnetic field depends on the amount of current and the distance from the wire.
○ The direction of the magnetic field around a wire can be determined using the
right-hand rule: Point the thumb of your right hand in the direction of the current,
and your fingers will curl in the direction of the magnetic field.
2. Electromagnetic Induction:
○ Faraday’s Law: A changing magnetic field induces an electric current in a wire.
This is the principle behind generators.
○ Generators: Convert mechanical energy into electrical energy using
electromagnetic induction.
○ Transformers: Devices that change the voltage of alternating current (AC) using
electromagnetic induction.
3. Applications of Electromagnetism:
○ Electric Motors: Convert electrical energy into mechanical energy.
○ Transformers: Change voltage levels in AC circuits for efficient power
transmission.
○ Magnetic Levitation: Uses magnetic fields to lift objects (like in maglev trains).
Key Terms:
● Electric Charge: A property of matter that causes it to experience a force when placed
in an electric or magnetic field.
● Current: The flow of electric charge in a conductor.
● Voltage: The energy per unit charge provided by the power source in a circuit.
● Resistance: The opposition to the flow of electric current in a conductor.
● Magnetic Field: A field around a magnetic object where magnetic forces are exerted.
