What is a zener diode? Give its symbol.

What is magnesia cement? Give 'its composition?

If the mass percent of various elements of a compound' is known, its empirical formula can be calculated What is mass percent? Give its mathematical expression

What is pigeon's milk? Give its function.

If the mass percent of the various elements of a compound is known, its empirical formula can be calculate. What is mass percent?Give its mathematical expression.

What is resistivity?Give its unit.