Electricity

• Ammeter measures the amps

  
• Diode allows current to flow in one direction

  
• LDR is when the resistance decrease when the light intensity increases
• LED is a diode that gives out light when current flows through it

  
• thermistor makes the resistance decrease when the temperature increases

  
• Voltmeter measures potential difference across a component

  
• Fixed resister provides resistance to the flow of current

  
• Variable resistor provides a changeable resistance value and is used to control the current flowing through the circuit

  
• Fuse is a device that melts when the current is too high and stops the flow of electricity

  
• Series has the same current but potential difference splits
• parallel circuits have same potential difference but the current splits
• DC is direct current, the current flows in one direction only
• AC is alternating current, the current is constantly changing direction
• Charge = current x time (Q = It)
• (V = IR). Potential difference = current x resistance
• current is the rate of flow of charged particles past a point
• frequency in Uk is 50Hz
• Uk potential difference is 230V
• why resistance of filament lamp increase as temperature increase

  ions vibrate more with increasing temperature, the ions obstruct the flow of electrons. Electrons will move more slowly causing smaller current
• Diode graph

  
• Resistor Graph

  
• Filament graph

  
• greater length means that there is more resistance and lower the current
• low resistance wires means less energy is lost as current flows through circuit
• live wire is brown, carries voltage from mains to appliance
• Neutral wire is blue and completes the circuit
• Earth wire is green and yellow stripes. safety wire used to stop appliance becoming live,
• Earth wire has low resistance meaning that the current will go from casing to the ground through the wire
• Like charges repel
• opposite charges attract
• Insulators do not conduct electricity because fixed electrons can’t flow through material
• two insulators can be charged by friction
• conductors stay neutral if rubbed together because electrons flow freely between them
• positive static charge forms an object that loses electrons
• negative static charge forms an object that gains electrons
• spark is when charge jumps through the air from negative object to positive object
• dangers of sparks: ignition of flammable materials, ignition of explosive material
• E = P x t
• P = VI
• watts = joules/seconds