# GCSE Physics Edexcel P2a Revision

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• Physics Revision
• Atomic Structure
• The nucleus is in the center of the atom, containing the protons and neutrons.
• The electrons are in the shells surrounding the atom.
• Charged Particles
• Neutrons have a mass of 1 and a neutral charge of 0.
• Protons have a mass of 1 and charge of +1 (positive)
• Electrons have a mass of 1/200 and a charge of -1 (negative).
• Effect of charged particles
• Ballons can stick to walls by electrons scraping from the clothes to the Balloon.
• A charged Comb can pick up small pieces of paper by transferring the electrons to the comb
• Electrical measurement
• The Ammeter
• Measures the current  (in amps) flowing through the compound.
• Must be placed in series (connected in a line with the component)
• The Voltmeter
• Measures the voltage or potential difference (in volts) across the component.
• Must be placed in parallel around the component under test - NOT around the variable resistor or the cell.
• Energy Calculations
• Charge = Current x time.
• Potential Difference = current x resistance.
• Speed = Distance/ Time
• Acceleration = Change in velocity/ Time taken .
• Resistance
• Resistance is anything in the circuit which slows the flow down.
• If you increase the voltage - then more resistance will flow.
• If you increase the resistance - then less current will flow.
• Graphs + Data
• Voltage-current Graphs
• Fixed Resistors
• Filament Lamp
• Diode