A2 Applied Science


Digital thermometer.

Digital thermometer.

  • Resistors slow the current down.
  • There is a thermistor in the digital thermometer-therm=heat, istor=risistor.

4 marks in exam question.

  • The resistance of the thermistor depends on the temperature it's being exposed to.
  • As the temperature changes, the resistance changes, so the current changes.
  • The greater the change in temperature, the greater the change in resistance.
  • The thermometer is calibrated so the current reading is converted into a temperature reading on a digital display.
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Body temperatures.

Body temperatures.

  • hypo=low
  • hyper=high

25C = death

32C = hypothermia

36.8 = core body temperature

36.5C-37.2C = body can survive

37.2C = fever

38C = hyperthermia

43C = death

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Measuring body temperature.

Measuring Body temperature.

Body temperature can be measured in; ear, mouth, rectum, forehead, armpit.

Glass thermometer.

  • Mercury expanding in a graduated capillary tube as the temperature increases.
  • Not commonly used as mercury is poisonous.

Ear thermometers.

  • Infra-red sensor (thermopile) measures the infra-red radiation emitted by the ear drum.
  • Hotter the object, more radiation is emitted.
  • Accurate and safe (doesn't touch the eardrum.

Forehead plastic temperature strips.

  • Thin flat piece of plastic, coloured liquid crystals.
  • Safe, easy to use, not accurate.
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  • 10C or lower, water below 15C.


  • Shivering.
  • Cold, pale, blue-grey skin.
  • Lack of interest.
  • Numb hands and fingers, difficulty performing tasks.

Late symptoms.

  • Slow pulse.
  • Stop shivering.
  • Loss of consciousness.
  • Slow breathing.
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  • Over heating leads to heat exhaustion which leads to heatstroke then death.


  • Mental changes.
  • Red, hot, dry skin.
  • Excessive sweating

Late symptoms.

  • Sweating stops because they're too dehydrated
  • severe dyhydration.
  • Organs stop functioning.
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Use of X-rays

Use of X-rays.

  • High frequency
  • Can cause cancer and other abnormalities
  • High cell density areas are most prone-brain, heart, ovaries, testes-prolific cell division
  • The higher the dose, the greater the chance of negative side effects
  • Rate at which the x-ray is received by the patient will have an effect.
  • Can have a high resolution image with a low dose due to technology advances
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Link between the dose size and side effects

Stochastic effects.

  • Random
  • Aren't related to the size of the dose
  • Don't have a threshold, (not affected by the dose size)
  • Actual effect isn't dependent on the size of the dose.
  • Show up years after exposure-cancer

Non-stochastic effects.

  • Related to the size of the dose
  • More severe with an increased dose
  • Has a threshold, (the effect wont occur unless the dose exceeds a certain value
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This is more physics than biology...

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