Why do we prefer to use a wrench with a long arm?

Why do we prefer a potentiometer with longer wire?

Why do we prefer mercury in a barometer?

Draw the circuit diagram of a common emitter n-p-n transistor as an amplifier. Would you prefer to use a transistor as a common base or a common emitter amplifer and why?

Why do we use ball-bearings?

Why do we need Quantum theory?

Why does chemist prefer to refer concentration of solution in terms of molality?