Why are inner pulleys in a block and tackle system smaller than others?

 Answer: 

Inner pulleys are smaller than others to eradicate the frictional force between the ropes and inner pulleys while in use.

Spanner has a long handle. Why?

Answer: When perpendicular distance between the force and the axis of rotation is large, smaller force is required to produce  the desired torque.

TERMINAL VOLTAGE

Terminal voltage of a dry cell is 1.3 V. It means that the cell can supply 1.3J of energy to move unit positive charge across its terminals in the external circuit connected to the cell.

EMF of a dry cell

Emf of a dry cell is 1.5 V. It means that the cell can supply 1.5 joule of energy to move 1 coulomb of charge all around the circuit ( outside and inside  the cell).