Current and Circuit Symbols

• Electric current is the flow of electrical charge around a circuit
• Unit for current = Amperes (A)
• Current can only flow in a closed circuit
• Potential difference = the driving force that pushes charge around
• Potential Difference unit = Volts (V)
• Resistance = restricts the charge to flow through the circuit
• Resistance units = Ohms
• The current depends on the potential difference across it and the resistance
• The greater the resistance the smaller the current can flow through if there's a potential difference
• A longer, thinner wire restricts the flow of charge
• Total charge (C) = Current (A) X Time (s)
• Q = IT
• More charge flows through when a bigger current flows
• A battery charger passes a current of 2A through a cell over a period of 2.5 hours. How much charge is transferred to the cell?

  18000 C
• What is this?

  Cell and battery

  
• What is this

  Open switch and closed switch

  
• What is this?

  Filament lamp and resistor

  
• What is this?

  Light emitting diode

  
• What is this?

  Resistor and variable resistor

  
• What is this?

  Ammeter and Voltemeter

  
• What is this?

  Diode and Light dependent resistor

  
• What is this?

  Thermistor

  
• A fuse (a rectangle with a line through) is a thin wire that melts when too much current is flowing
• Motor - converts electrical energy to sound
• Polarity. Every cell and battery has a positive (+) terminal and a negative (-) terminal.