L1. Electrical Charges & Fields_STUDENT

Electric Circuits

Introduction to Electricity

  • Electricity: A phenomenon involving stationary or moving electric charges.

Key Words

  • Potential Difference (Voltage) - measured in volts (V)

  • Current - measured in amperes (A)

  • Series and Parallel Circuits - configurations for circuits

  • Static Electricity - charge at rest, produced by friction

  • Generators - devices that convert mechanical energy to electrical energy

  • Batteries - sources of stored electrical energy

  • Switch - a device used to open or close an electrical circuit

Basic Concepts of Electricity

  • Static Electricity:

    • Stationary electric charge, typically produced by friction between insulators.

    • An object gaining electrons becomes negatively charged; one losing electrons becomes positively charged.

    • Attraction occurs between charged and uncharged objects while like charges repel.

Electric Fields

  • A charged object creates an electric field, strongest near the charge and weaker as distance increases.

    • Negative charges move toward positive regions due to electric fields.

Subatomic Particles in Electricity

Components of Atoms

  • Nucleus: Central part of the atom containing protons and neutrons.

  • Electrons: Negatively charged particles orbiting the nucleus.

  • Protons: Positively charged particles in the nucleus.

  • Neutrons: Neutral particles in the nucleus.

Charge and Current

  • Electric Current: Flow of charged particles, typically free electrons in metal conductors.

    • Depends on potential difference and total resistance in a circuit.

    • Measured in coulombs (C); charge of an electron is approximately 1.6 x 10^-19 C.

Key Relationships

  • Charge (Q) in a circuit is calculated using the formula:

    • [ Q = I \times t ]

  • Where:

    • Q = charge in coulombs (C)

    • I = current in amperes (A)

    • t = time in seconds (s)

  • Example: If a current of 10 A flows for 30 seconds, [ Q = 10A \times 30s = 300C ]

Investigations of Static Electricity

Investigation Examples

  1. Human Hair and Balloon: Rub balloon on hair to see if it stands or sticks to a wall.

  2. Can and Balloon: Charged balloon can move a nearby can.

  3. Tissue Paper and Balloon: Observe if the charged balloon picks up small pieces of paper.

  4. Bending Water with Balloon: See if the balloon can bend a stream of water.

  5. Moving Straw: Using a straw to see if it moves when charged.

Electrical Charge in Circuits

Resistance

  • Measured in ohms (Ω).

  • Total resistance in series circuits is the sum of individual resistances:

    • [ R_{total} = R_1 + R_2 + R_3 ]

Series vs. Parallel Circuits

Series Circuits

  • Current is the same throughout; voltage divides across components.

Parallel Circuits

  • Current splits between branches, potential difference remains the same across components.

  • Higher current available can make components brighter or functional in parallel.

Special Components in Circuits

Diodes and LEDs

  • Diode: Allows current flow in one direction.

    • Used for signal processing.

  • Light Emitting Diode (LED): A diode that emits light when current flows through it.

  • LDR (Light Dependent Resistor): Changes resistance based on light level, used in automatic lights.

Thermistors

  • A type of resistor that varies in resistance with temperature; applied in systems like thermostats.

Important Equations

  1. Charge: [ Q = I \times t ]

  2. Voltage in Series: [ V_{total} = V_1 + V_2 + V_3 ]

  3. Resistance: [ R = V/I ]

Summary

  • Understanding the concepts of electricity is crucial for analyzing circuits.

  • Conductors allow for the flow of electric current, and components like resistors, diodes, and batteries play key roles in controlling and utilizing electricity.