A2 Applied Science

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.

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

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.

Hypothermia.

• 10C or lower, water below 15C.

Symptoms.

• 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.

Hyperthermia.

• Over heating leads to heat exhaustion which leads to heatstroke then death.

Symptoms.

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

Late symptoms.

• Sweating stops because they're too dehydrated
• severe dyhydration.
• Organs stop functioning.

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

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