The lowest temperature at which a substance catches fire is called its_____.

After using for some time, big transformers get heated up. This is due to the fact that

$1.$ current produces heat in the transformers.

$2.$ hysteresis loss occurs in the transformers.

$3.$ liquid used for cooling gets heated.

Select the correct answer using the code given below:

The instrument used to regulate temperature to a particular degree is called:

1. Thermostat

2. Thermometer

3. Pyrometer

4. Thermocouple