Current, potential different and resistance

• What is this symbol

  Lamp

  
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  Fuse

  
• What is this symbol

  Voltmeter

  
• What is this symbol

  Ammeter

  
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  Thermistor

  
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  LDR

  
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  Open switch

  
• What is this symbol

  Closed switch

  
• What is this symbol

  Cell

  
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  Battery

  
• What is this symbol

  Diode

  
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  Resistor

  
• What is this symbol

  Variable resistor

  
• What is this symbol

  LED

  
• For electrical charge to flow through a closed circuit the circuit must include a source of potential difference
• Electric current is a flow of electrical charge
• The size of the electric current is the rate of flow of electrical charge.
• What is the equation for charge flow


  Charge flow= current x time
• A current has the same value at any point in a single closed loop .
• The greater the resistance of the component the smaller the current for a given potential difference across the component.
• Define a switch


  A switch used to turn a circuit on (closed) and off (open).
• Define a lamp


  An electrical current heats the filament in a bulb so that it gives out light.
• Define a Fixed resistor


  A resistor restricts or limits the flow of electrical current. A fixed resistor has a resistance that does not change.
• Define a Variable Resistor


  Moving the position of the slider on this resistor, changes the resistance. A variable resistor is used in some dimmer switches and volume controls.
• Define a Thermistor


  The resistance of a thermistor depends on its temperature.

  • Low temperatures = high resistance
  • As the temperature increases = the resistance decreases.
  • A thermistor can be used in thermostats or heat activated fire alarms
• Define a Light- Dependent resistor (LDR)


  The resistance of a LDR depends on light intensity.

  • Low light levels = high resistance
  • Light intensity increases = Resistance decreases
  • A LDR can be used as a sensor in cameras or automatic lights that come on when it gets dark.
• Define a Semiconductor diode


  A semiconductor diode allows current to flow in one direction only. Current will not flow in the other direction. Diodes are used to convert an alternating current into a direct current.