Electricity

• What is electric current? Current or electric current is the flow of electrical charge.
• What is resistance? Resistance is a measure of the opposition to current flow in an electrical circuit.
• What is potential difference measured in? Volts (V)
• What happens if the resistance is increased? The greater the resistance across a component, the smaller the current that flows.
• " Battery
• " Cell
• " Ammeter
• " Resistor
• " Diode
• " LDR (Light Dependent Resistor)
• " Bulb
• " Thermistor
• Formula for potential difference, current and resistance V = IRPotential Difference (V) = Current (A) X Resistance (Ω)
• Formula for energy, power and time E = PtEnergy (J) = Power (W) x Time (s)
• Formula for power, current and resistance P = I^2RPower (W) = Current (A)^2 x Resistance (Ω)"
• Formula for power, current and potential difference P = VIPower (Watts) = V (Volts) x I (Current)
• How do you calculate the total resistance in a series circuit? Sum of all the resistor's resistance
• Example of a parallel circuit "
• What happens to the current in a parallel circuit? The current in a parallel circuit is shared between the components
• What happens if you add a resistor or component in a parallel circuit? In a parallel circuit, the net resistance decreases as more components are added, because there are more paths for the current to pass through
• What is the National Grid? A giant system of cables and transformers that covers the UK and connects power stations to consumers
• Why does the National Grid use transformers? To transfer energy in the most effecient way because a high current makes you lose loads of energy. It is cheaper to boost the potential difference really high (400 000 V) and keep the current low.
• Diagram of a wire  "
• What is the neutral wire used for? Completes the circuit an carries away current (0V)Electricity normally flows in through the live wire and out through the neutral wire
• What is alternating current? Alternating current is current that is constantly changing directione.g (Electricity in your home)
• How do you calculate efficiency? "
• How is a positive static charge caused? Protons and neutrons cannot move from object to object, so electrons move away elsewhere, causing less negative charge.
• Examples of how to create static electricity  Rubbing ruler/balloon on head
• LDR Graph "
• Explain how the resistance of a filament lamp changes as the potential difference across it As the potential difference across the filament lamp increases the current across the lamp also increases due to Ohm's law.The increase in current flow also causes the lamp to heat up which causes the resistance of the lamp to also increase.
• What does more energy efficient mean? A higher proportion / percentage of the total energy input is usefully transferred
• What is an electric field? A region in which a charged object will experience a non-contact electrical force
• All 6 formulas Q = ITE = PTE = QVV = IRP = VIP = I^2 R
• What does a step down transformer do? A step down transformer increases the current and lowers the voltage.
• Why does a Van de Graaf generator make your hair stand up? Each strand of hair picks up the same charge and repels each other.
• What is the purpose of a fuse in a circuit? The fuse breaks the circuit if a fault in an appliance causes too much current to flow.
• How can you get an electrostatic shock? "
• What does a thermistor do? A thermistor is a component where resistances changes with its temperature.
• Example of a use of a thermistor  To turn a heater off when a house reaches certain temperature
• What is a rectifier? A component that turns alternating current into direct current