Electricity

• Current is the flow of electrical charge
• Current is measured in amps (A)
• Potential Difference is measured in Volts (V) and is the work done per unit charge.
• Resistance is measured in ohms (Ω) and is a measure of how difficult it is for current to flow through a component
• Charge Flow= Current x Time (Q=IT)
• Potential Difference= Current x Resistance (V=IR)
• Ohmic Conductors have a constant resistance
• LDR= Light Dependent Resistor, a resistor that changes resistance in proportion to the light intensity
• In Bright light, resistance in an LDR increases and current decreases.
• In darkness, the resistance in an LDR is very high, so the current is very low
• Thermistor: an electrical resistor whose resistance is greatly reduced by heating, used for measurement and control.
• In hot conditions, resistance in a Thermistor decreases as the temperature increases.
• In cold conditions, Resistance in a Thermistor increases as the temperature decreases.
• LDR's and Thermistors can be used in Sensing Circuits
• The voltage across the variable resistor will change depending on the amount of energy detected by it
• In a Series Circuit, if one component is removed, the circuit is broken
• Potential Difference is shared in a series circuit
• Current is the same everywhere is a Series Circuit
• Resistance adds up in a Series Circuit
• In Parallel Circuits,if you remove one component, the others are hardly affected
• Potential Difference is the same everywhere in a Parallel circuit
• Current is shared in a Parallel circuit
• Adding a resistor in parallel reduces the total resistance
• Mains Supply is AC, Battery Supply is DC
• UK Mains Supply is 230V
• UK Frequency of Main's Supply is 50Hz
• Most cables have 3 wires
• Live Wire is brown and provides alternating current to the appliance.
• Earth Wire is green and yellow and is for safety, it prevents the appliance from becoming live
• Neutral Wire is Blue and completes the circuit and has no charge like the the Earth Wire
• Live Wires can give you an electric shock
• Energy Transfer depends on Power
• Energy Transferred = Power x Time (J)
• Power Ratings are the maximum amount of power they can operate at safely
• Energy Transferred= Charge Flow x Potential Difference
• Power= Potential Difference x Current
• Electricity is distributed by the National Grid
• Electricity Production must meet demand
• The National Grid distributes electricity from large-scale generators to local distribution networks.
• Transformers increase or decrease voltage depending on where it's going.