Question

Supriya was doing an experiment (comparison of emf's) using potentiometer in physics lab. She could not take the reading because the galvanometer showed the same side deflection. She checked the circuit and the connections were correct. Her friend Manasa who was doing her experiment nearby came to help Supriya. Manasa increased the voltage of the eliminator (by turning the knob) supplying current to the potentiometer. Supriya tried the experiment again and got the reading. She thanked Manasa for her help.
(a) State one reason why the galvanometer showed the same side deflection.
(b) Distinguish between emf and terminal potential difference.

Answer 1

Hint: This question requires the conceptual and experimental knowledge of experiments related to electromotive force. Galvanometer, indicated in the above question, is a device used to measure electric current. A Potentiometer is a device which is used to provide variable voltage.

Complete step by step answer:
(a) For the galvanometer to show deflection in the opposite direction, the emf of the driving cell should be greater than the emf of the experimental cell. So, when Manasa increases the voltage from the potentiometer, the galvanometer shows deflection in the opposite direction.
(b) Emf: It is the potential difference between the terminals of a cell in an open circuit.
Potential difference: It is the voltage across the terminals of the cell when the circuit is closed.

Note: The electric potential produced by an electrochemical cell or by changing the magnetic field is known as electromotive force. Electromotive force is commonly abbreviated as EMF. Energy is converted from one type to another using a generator or a battery.