There are many ways to test and identify metal. The easiest way is observing its color. Also how reflective it is. Other ways would be boiling point, melting point, density, or conductivity of the metal.
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Light bulb -it produces heat and light
toaster - it produces heat and the metal strips glow producing light
The lac repressor protein binds to the operator when it is active. The lac repressor is a protein or a DNA-bounding protein as it is called. The lac repressor also involves the lactose metabolism and it is also responsible for the transcription of three lac genes.