Question

When a high resistance voltmeter is connected directly across a resister its reading is 2 V. An electric cell is sending the current of 0.4A, (measured by an ammeter) in the electric circuit in which a rheostat is also connected to vary the current.

Name and state the law applicable in the given case. A graph is drawn between a set of values of potential difference (V) across the resister and current (I) flowing through it. Show nature of graph thus obtained.

Answer 1

The law applicable here is Ohm’s Law.

It states that the current flowing through a conductor is directly proportional to the potential difference across the conductor 

I ∝ V.

The proportionality constant is the resistance of the conductor; it is constant for the known range of the temperature. 

V = IR. 

The Graph obtained is the straight line with positive slope passing through the origin as shown in the figure below.