1. Why is Kirchoff”s law preferred over Ohm’s law?
Ans: In ordinary conditions, ohm’s law is used for analyzing and measuring the current and voltage of the circuit. But, there are several complex cases, in which Ohm’s Law cannot be used to measure the current and voltage. In such circuit, Kirchhoff’s law is used.
2. Explain Kirchoff’s laws.
Ans: There are two laws given by Kirchhoff.
1st law: The algebraic sum of current at a junction of electric current is always zero.
i.e.,∑I = 0
2nd law: In a closed loop, the sum of emf is equal to sum of product of current and resistance.
i.e.,∑E = ∑IR
3. We prefer potentiometer to measure emf of a cell than voltmeter. Why?
Ans: When a voltmeter is used to measure the emf of a cell, it draws some amount of current from the cell. So, the reading shown by a voltmeter is always less than the exact emf of the cell. But, potentiometer doesn’t draw any current from the cell. So, the reading shown by the potentiometer is more accurate than that of voltmeter. Therefore, we prefer potentiometer to measure the emf of a cell.
4. What is meter bridge? What is its principle?
Ans: It is an electrical device used to find the resistance of the object. It can also compare the resistance of two wires. Meter bridge work in the principle of Wheatstone bridge.
5. What is potentiometer? Why it is named so?
Ans: It is an electrical device that is used to measure the emf of a cell in very precise manner. It can also compare the emf of two cells and find the internal resistance of two cells. It is named so because it can measure the potential difference of two terminals of a cell.
6. Mention two applications of potentiometer?
Ans: The two applications of potentiometer are as follows:
- It is used to compare the emf of two cells.
- It is used to find the internal resistance of a cell.