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• The first major theory that had tried to explain what stuff is made out of was atomic theory
• Atomic theory


  The idea that everything is made up from tiny little particles that can't be broken down any further and that they're separated from each other by empty space
• John Dalton's atomic model


  Atoms as solid spheres, different types of spheres make up different elements
• J.J. Thompson proposed the plum pudding model


  1897
• Plum pudding model


  • Atoms contain negatively charged particles (electrons)
  • Atoms have a general ball of positive charge with discrete electrons stuck in it
• Rutherford and students made a big discovery


  1909
• Rutherford's experiment


  1. Fired positively charged alpha particles at a thin sheet of gold

  2. Some alpha particles were deflected to the side or back, proving the plum pudding model wrong
• Rutherford's nuclear model


  Atoms have a compact nucleus containing all the positive charge, with a cloud of negative charge around it
• Rutherford's nuclear model had a flaw - the negative electrons should collapse into the positive nucleus
• Niels Bohr suggested a solution


  1913
• Bohr's model


  Electrons orbit the nucleus in shells, preventing the atom from collapsing
• Further experiments by Rutherford found the positive charge in the nucleus is made up of protons
• James Chadwick provided evidence for neutral particles (neutrons) in the nucleus
• The current understanding of the atom is based on Bohr's model with a few small changes
• Fuse


  A component that melts and breaks the circuit if current flow exceeds a specific limit to protect the circuit.
• Diode


  A component that allows current to flow in one direction only, preventing backflow.
• Ammeter


  A device that measures the current flow in a circuit.
• Voltmeter


  A device that measures the potential difference (voltage) in a circuit.
• Fixed Resistor


  A component that restricts the flow of electric current to a constant amount.
• Variable Resistor


  A component that restricts the flow of electric current to varying degrees.
• LDR


  A component that changes its resistance based on the intensity of light.
• Thermistor


  A component that changes its resistance based on temperature.
• Fuse Purpose


  To protect the circuit by breaking the circuit when an excessive current flows through the circuit.
• Fuse Breaking Effect


  The circuit is interrupted, and the flow of current is interrupted when a fuse breaks.