- 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.
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.
Measuring Body temperature.
Body temperature can be measured in; ear, mouth, rectum, forehead, armpit.
- Mercury expanding in a graduated capillary tube as the temperature increases.
- Not commonly used as mercury is poisonous.
- 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.
- 10C or lower, water below 15C.
- Cold, pale, blue-grey skin.
- Lack of interest.
- Numb hands and fingers, difficulty performing tasks.
- Slow pulse.
- Stop shivering.
- Loss of consciousness.
- Slow breathing.
- Over heating leads to heat exhaustion which leads to heatstroke then death.
- Mental changes.
- Red, hot, dry skin.
- Excessive sweating
- Sweating stops because they're too dehydrated
- severe dyhydration.
- Organs stop functioning.
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
Link between the dose size and side effects
- 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
- 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