Electromotive Force and Internal Resistance

The video tutorial explains the concept of electromotive force (EMF) in electric cells, defining it as the work done by a non-electrical force to move a unit positive charge from the negative to the positive pole. The unit of EMF is the volt. It also covers the internal resistance of a cell, which is influenced by factors such as the distance between electrodes, the area and size of electrodes, the strength of the electrolyte, and temperature. The tutorial further discusses terminal voltage, explaining that in an open circuit, the terminal voltage equals the EMF, as no current flows through the electrolyte. The role of an ideal voltmeter in measuring EMF is also highlighted.

What is the unit of electromotive force (emf)?

• Watt

• Joule per coulomb

• Newton

• Ampere

Which of the following is true about the emf of a cell?

• It is always zero

• It is the energy gained by a unit positive charge

• It is the same as the internal resistance

• It is measured in amperes

What is the role of a non-electrical force in an electric cell?

• To decrease the internal resistance

• To measure the terminal voltage

• To move a unit positive charge from negative to positive pole

• To increase the temperature

Which of the following factors does NOT affect the internal resistance of a cell?

• Distance between electrodes

• Color of the electrodes

• Area and size of electrodes

• Strength of the electrolyte

How does temperature affect the internal resistance of a cell?

• Increases with temperature

• Decreases with temperature

• Remains constant

• Fluctuates randomly

What instrument is used to accurately measure the internal resistance of a cell?

• Potentiometer

• Voltmeter

• Ammeter

• Ohmmeter

In an open circuit, what does the terminal voltage equal?

• Current through the cell

• Zero

• Internal resistance

• Emf of the cell

Why does an ideal voltmeter read the emf of a cell in an open circuit?

• It has infinite resistance

• It is connected in series

• It has zero resistance

• It draws maximum current

What happens to the terminal voltage when no current flows through the electrolyte?

• It becomes negative

• It doubles

• It equals the emf

• It becomes zero

What is the effect of connecting an external resistance across the terminals of a cell?

• Increases the emf

• Decreases the emf

• Changes the terminal voltage

• Has no effect