• Using a Thermistor to Make a Fire Alarm

    responds to temperature by lowering its electrical resistor. The transistor can be used in a circuit to switch on a fire alarm. When a fire is lit, the thermistor gets hotter and the resistance of the thermistor decreases. The voltage across the...

  • Making a Seat Belt Alarm With Logic Gates

    We can use logic gates to stop car drivers and their passengers forgetting to put their seat belts on. The circuit below will not allow the ignition switch start the car unless the seat belt(s) are fastened. To start the car both the ignition and the...

  • University Maths Notes - Game Theory

  • University Maths Notes - Logic

  • Table of Properties of Alpha, Beta and Gamma Radiation

    will escape from the body if ingested so this is the least dangerous form of radiation. Uses Alpha radiation is used in fire alarms. If smoke enters the detector, the amount of radiation leaving the sensor will fall significantly and the alarm will be...

  • Nuclear Waste

    of sources. The radioisotopes used in medicine, the nuclear fuel used in atom bombs – even the tiny samples used in smoke alarms all generate waste. Most waste however – about 95% - is produced by nuclear power stations, and may half lives of tens of...

  • The Reed Switch

    the current stops flowing. This is a normally closed reed switch, shown below. Normally closed reed switches can be used as alarms.

  • Transducers

    an output which is fed to another transducer and changed into some useful output or signal. Often this is so that an alarm can be sounded or something can be switched on or off automatically. The basic arrangement of such circuits is shown below. Input...

  • Uses of Alpha Radiation

    amount of radiation reaching the detector. When the detector senses that the amount of radiation reaching it has fallen, the alarm is triggered. Alpha radiation has another, more sinister use. When the Russian government wishes to assassinate someone,...

  • Hysteresis

    under the hysteresis loop - and time delays – it takes time to magnetize and demagnetize a material, so for example in an alarm bell an electromagnet may continue to attract the armature when the applied electric current to the operating coil is removed...


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