IGCSE Edexcel physics electricity question and answer | graded A+

IGCSE Edexcel physics electricity question and answer | graded A+ current amps (A) Charge Coulombs (C) Energy Joules (J) Resistance Ohm (Ω) time second (s) Voltage Volts (v) Power watt (W) Series circuit rules current Current is the same everywhere - ammeter readings are the same Current depends on the applied voltage + the no and nature of other components Series circuit rules voltage and general Voltage is shared between components that are the same Control all components with one switch The more bulbs added the dimmer Bulbs break - whole circuit does not work Parallel circuit rules current Current splits at each branch equally if the components are the same Parallel circuit voltage and genera Voltage is same as total voltage across each branch Voltage across 2 components connected in parallel is the same Can include a switch to control each branch independently of others If one bulb breaks, others keep working Every branch has the same voltage so brightness stays the same Current/voltage filament shape S shape Resistant of a filament increases as the temperature of the filament increases Reversing the voltage (negative values on graph) reverses the direction of the electric current but not the shape of the curve Does the lamp obey ohms law? No Current voltage graph of a fixed resistor Straight line through the origin What is ohms law? Current is proportional to the voltage Does the wire or fixed resistor obey ohms law? Yes What does a diode do? Current flow only flows through a diode in one direction Has very high resistance in the reverse direction What is resistance? A measure of how hard it is for the current to flow All devices have some resistance - a resistor is a device that has a particular resistance Increasing the resistance will decrease the current you can do this by adding more components or ones with higher resistance Resistance of thermistor The resistance of a thermistor decreases as the temperature increases The higher temperature line therefore has a greater slope than the lower temperature case Resistance of light dependant resistor The resistance of a light dependant resistor decreases as light intensity increases The bright light line therefore has a greater slope than the dim light case What is electric current The rate of flow of electric charge What can lamps and leds can be used to do? Indicate the presence of a current in a circuit What do metallic conductors do? Copper wire electrons carry negative charge from the negative side of a power supply, around a circuit and back into the positive side What happens in parallel circuits? Total amount of current flowing into the junction or split is equal to the total current flowing out Conductor Material through which electric current flows easily Insulator Have a very high resistance to the flow of electric current Examples of conductors Copper Steel Graphite Mercury examples of insulators Paper Rubber Plastic Diamond What happens when insulating materials are rubbed against each other? They become electrically charged What happens in term of electrons? Electrons are rubbed off one material onto the other The material that gains electrons becomes negatively charged The material that loses electrons is left with an equal positive charge What attracts and repel? Forces of attraction between unlike charges Forces of repulsion between like charges What is electrostatic phenomena When static electricity has an imbalance of electric charges in a material has a specific effect Electrons move from one material to another What do materials with a negative charge want to do? Want to earth its charge Uses of electrostatic charges Photocopiers - light reflects off paper onto positively charged drum, black toner doesn't reflect so the drum keep its charge in these areas, black toner is pressed onto paper Paint sprayers - as paint droplets leave they repel each other and spread out to form a fine cloud of paint, the negatively charged metal attracts the positively charged paint Dangers of electrostatic charges Refuelling aircrafts - if the fuel in the hose built up an electric charge, a spark might form and ignite the fuel (hoses earthed to prevent this) Tankers - transporting liquid chemicals in ship tanks can build up static electricity causing a spark and igniting the liquid