Viva Voce: Ohm’s Law | Lab Manuals for Class 10 PDF Download

Q.1. What do you understand by the term ‘terminal potential difference of a cell’?

The potential difference which exists across the terminals of a cell when current is being drawn from the cell, is known as terminal potential difference of a cell.

Q.2.  What do you understand by the term ‘resistance’ of a conductor?

The resistance of a conductor may simply be explained as being the obstruction offered to the passage of electric current by the conductor in the circuit.

Q.3. What is the composition of nichrome alloy?

The composition of nichrome alloy are as follows:
Ni = 68%
Cr = 15%
Fe = 15.5%
Mn = 1.5%

Q.4. What do you mean by a battery eliminator?

A device which is used in place of battery or cells, is known as a battery eliminator.

Q.5. Suppose in this experiment, you see that the deflection on ammeter (or voltmeter) scale goes beyond the full scale. What will you infer from such an observation? What will you infer, if the deflection takes place in opposite direction?

If the deflection goes beyond full scale, a higher range of ammeter is required for the circuit. And deflection in opposite direction indicates that terminal has not been joined properly and it should be reversed.

Q.6. Suppose the ammeter (or voltmeter) you are using in this experiment do not have positive (+) and negative (-) terminal markings. How will you use such ammeter (or voltmeter) in the circuit? 

First of all we connect ammeter or voltmeter arbitrary in the circuit, if deflection occurs in opposite direction. It means the connection is not proper. Now by interchanging the terminals, we can use it in the circuit.

Q.7. What do you understand by the term ’emf of a cell’?

The maximum potential difference which exists across the terminals of a cell when no current is drawn out of the cell is called emf (electromotive force) of a cell.

Q.8. Can you explain why there is no current in the circuit, if plug is removed?

As we know air gap gives infinite resistance to the circuit. So, if the plug is removed, there will be no current in the circuit.

Q.9. What are the necessary conditions for current flow through the conductor?

There are two such conditions:

• There must be a closed circuit.
• There must be a source of electrical energy.

Q.10. Why is it advised to clean the ends of connecting wires before connecting them? 

Ends of wire should be cleaned to remove the insulation (or insulating layer) of dust particles since, presence of insulation (which is a non-conducting material) wilt not allow current to flow in the circuit.

Q.11. If the resistor of known resistance value is replaced with a nichrome wire of 10 cm length. How do the values of current through the nichrome wire and potential difference across the two ends of it may change? How the values will change, if the replaced wire is of manganin in place of nichrome?

Nichrome wire offers more resistance. So, value of current decreases, while value of potential difference across the wire increases. As manganin offers less resistance than nichrome so, value of current increases and potential difference decreases.

Q.12. In this experiment, it is advised to take out the key from the plug when the observations are not being taken. Why?

It is to avoid the unnecessary heating of wires. Heating may change the resistance of resistors.