State Ohm's law. what is the necessary conditions for its validity. how is this law varied experimentally?
Ohm’s law states that the current flowing through a conductor is directly proportional to the potential difference across the conductor. The proportionality constant is the resistance of the conductor, it is a constant for a known temperature range.
An activity:
Connect the wires as shown in the diagram. Increase the rheostat to increase the current in the circuit, obtain the value of current in the circuit by the ammeter and also find the potential difference using the voltmeter. For increase in current see the brightness of the bulb connected. Use your knowledge so far to obtain the resistance of the bulb.
Graph of Ohm’s law is a straight line obtained when current in the circuit (I) is plotted along x axis and potential (V) along y axis.
In varying temperature conditions ohm's law does not hold good.
Under constant temperature and other physical conditions like pressure etc. ohm's law is valid. If temperature is varied resistance of a conductor varies which doesn't provide desired result.
Regards