Current & Circuit Symbols

• Current is the flow of electrical charge
• Electric current is a flow of electrical charge
• Electrical charge will only flow round a complete (closed) circuit if there is a potential difference, so a current can only flow if there's a source of potential difference
• The unit of current in the ampere, A
• In a single, closed loop the current has the same value everywhere in the circuit
• T or F: Electrical charge can flow through a circuit without a potential difference. F

  
• Potential difference (voltage) is the driving force that pushes the charge around
• The unit for voltage is the volt, V
• Resistance is anything that slows the flow of electrons
• The unit for resisance is the ohm, Ω
• The current flowing through a component depends on the potential difference across it and the resistance of the component
• The greater the resistance across a component, the smaller the current that flows (for a given potential difference across the component)
• Total charge through a circuit depends on current and time
• The size of the current is the rate of flow of charge
• When current flows past a point in a circuit for a length of time then the charge that has passed is given by the formula: Q(Charge flow (C)) = I(Current (A)) x t(Time (s))
• More charge passes around the circuit when a larger current flows
• A battery charger passes a current of 2.0 A through a cell over a period of 2.5 hours. How much charge is transferred to the cell?


  Q = I x t -> 2.0 x (2.5 x 60 x 60) = 18,000 C
• What is symbol is V called?

  Cell

  
• What is symbol is I called?

  Wire

  
• What is this symbol of?

  Battery

  
• What does this symbol represent?

  Open switch

  
• What does this symbol represent?

  Closed switch

  
• What does this symbol represent?

  Bulb

  
• What does this symbol represent?

  Fuse

  
• What does this symbol represent?

  LED

  
• What does an LED stand for?

  Light Emitting Diode

  
• What does this symbol represent?

  Variable resistor

  
• What does this symbol represent?

  Ammeter

  
• What does this symbol represent?

  Volmeter

  
• What does this symbol represent?

  Diode

  
• What does this symbol represent?

  LDR

  
• What does LDR stand for?

  Light Dependant Resistor

  
• What does this symbol represent?

  Thermistor