Question :How is electric current related to the potential difference across the terminals of a conductor?
Draw a labeled circuit diagram to verify the relationship.
(ii) Why should an ammeter have low resistance?
(iii) Two V- I graphs A and B for series and parallel combinations of two resistors are as shown. Giving reason state which graph shows
(a) series, (b) parallel combination of the resistors.
The correct answer is -(i) Electric current is directly proportional to the potential difference across the terminals of a conductor. This relationship is given by Ohm’s law, which states that the current flowing through a conductor is directly proportional to the potential difference across its ends, provided the temperature and other physical conditions remain constant. Mathematically, this relationship is expressed as:
(ii) An ammeter should have low resistance because it should not significantly affect the current flowing through the circuit being measured. If the ammeter has high resistance, it will draw a large amount of current from the circuit, causing the measured value to be lower than the actual value. Hence, the resistance of an ammeter should be very low compared to the resistance of the circuit being measured.
(iii) In the V-I graph for a series combination of two resistors, the current flowing through both the resistors is the same. Hence, the graph shows a linear relationship between voltage and current. On the other hand, in the V-I graph for a parallel combination of two resistors, the voltage across both the resistors is the same. Hence, the graph shows a non-linear relationship between voltage and current. Therefore, graph A shows a series combination of resistors, while graph B shows a parallel combination of resistors.
