Voltage, Current, Pd and Graphs

• What is the equation that links Resistance,Current and Potential Difference

  V=IR

  V(potential difference in Volts)

  I(current in amps)

  R(resistance in Ohms)
• What happens to resistance if we increase temperatureof normal materials and resistors?

  Resistance increases when temp increases.
• The Filament Bulb Graph.

  Wire in bulb glows hot

  Heat increases so does resistance

  Curve less steep as resistance increases

  
• What does the filament bulb graph look like?

  
• What are Diodes?

  diodes are a conducting switch that has such a high resistance in a reverse direction that it forces the current only one direction.
• The Diodes Graph.

  Only shows positive as it doesn't allow current to reverse

  A small increase in voltage produces a huge increase in current

  O. 7v delay

  
• What is a thermistor

  A resistor that depends on heat

  Can be used for thermostats and car engines
• What is a fixed resistor

  A resistor that cannot change the amount of resistance

  
• What is a variable resistor

  A resistor that can easily adjust the amount of resistance

  
• ammeters are added in series, volt meters are added in parallel
• Light Emitting Diodes Emit light when current flows through forward
• LDR graph qualities

  • Resistance depends on light
  • if bright =high resistance
  • is dark=low resistance
• what are LDRs good for?

  Night lights
• What are thermistors goof for?

  Thermostats and car engines
• Thermistor Graph qualitiesTEMPERATURE

  Depends on heat

  when hot resistance decreases

  when cold resistance increases
• Thermistor TEMPERATURE Graph

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• What does the Diode Graph look like? 


  .

  
• In some materials what happens when temperature is increased?

  Electrons are freed From outer shell, meaning that it can carry a current when Pd is given.
• On a thermistor V I graph when temperature is high...

  Current is high, voltage is high and resistance is low.
• On a thermistor V I graph when temperature is low...

  Current is low, voltage is high, (?), resistance is high.
• On a graph if a resistor at constant temperature, voltage is directional proportional to current

  .

  
• LDR LIGHT DEPENDANT RESISTOR graph I V. 


  .

  
• On an LDR IV graph when it is bright... 


  Current and voltage increase and resistance decreases
• On an LDR IV graph when it is darker... 


  Current decrease and voltage decrease, (?) , because resistance has increased
• Why is V and I directionally Proportionate

  Increase in PD causes an increase in current
• In an IV graph, the steeper the gradient of the line (upwards) , the lower the resistance
• Why does current decrease when PD increases in a bulb graph?

  because in the bulb the metal has a changing resistance, the molecules in metal move more blocking the sea of electrons
• When temperature increased what would happen to the resistor

  The resistor will stay the same, because resistors are made from specific materials that resistance would stay constant even if the temperature changed
• LED have the same graph as what

  a normal diode
• What does a THERMISTOR do is temperature increases

  Resistance in a thermistor decreases
• What does an LDR do when light intensity increases

  resistance in a LDR decreases