Question

The resistance of a discharge tube is

• A. Non-ohmic
• B. Ohmic
• C. Zero
• D. Both B and C

Answer 1

The correct option is A

Non-ohmic

Explanation of the correct option:

In the case of option (A),

1. A discharge tube is a gas-filled tube comprising electrodes within a temperature-resistant envelope. They are majorly used in telecommunication equipment, frequency lines, etc.
2. The resistance of a discharge tube is high when it is turned off and low when it is turned on.
3. So, here, the potential difference $V$ does not vary linearly with the current $I$.
4. Hence, ohm's law is violated and it is considered a non-ohmic resistor.

Explanation of the incorrect options:

In the case of option (B),

1. In an ohmic resistor, the potential difference $V$ and the current $I$ follow a linear relationship.
2. Since the linear relationship does not exist for the discharge tube, thus, it is not an ohmic resistor.

In the case of option (C),

The resistance value of a discharge tube is not always zero. Thus, this is not the correct option.

Hence, option (A) is the correct answer.