Physics - Electricity 0.0 / 5 ? PhysicsElectricityIGCSEAQA Created by: Carys_ElizabethCreated on: 26-04-16 19:05 Charge, Current and Voltage Current The rate of flow or charge. Measured in Amperes (Amps). Coulomb The charge of 6x10^18 electrons. Every coloumb is an amount of negative charge equal to 6x10^18 electrons. If 6x10^18 electrons flow past a point in the time of 1 second then the current is equal to 1 amp. Potential Difference The amount of energy per unit charge (coulomb) Voltage The voltage of a battery is equal to the energy in joules provided when a charge of one coulomb passes through the battery. 1 of 3 Resistance The thinner the wire, the greater the resistance. This is because there is less space for electrons to move and there are more collisions between the electrons and ions. More frequent collisions mean the temperature of the wire increases. The higher the temperature of the wire, the higher the resistance. LDR resistance As light intensity decreases the resistance of LDR's increases. This means that they can be used effectively in street lights. Resistors Have constant resistance. Ohm's law states that the current through a resistor is proportional to the potential difference provided the temperature is constant. 2 of 3 Electricity equations energy transferred = potential difference x charge electric charge = current x time voltage = current x resistance electrical power = current x voltage 3 of 3
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