Question

Which of the following an ohmic resistance?

• A. Diode valve
• B. Filament of a bulb
• C. Carbon are light
• D. Manganin wire

Answer 1

The correct option is D

Manganin wire

Explanation for correct option(s):

(D) Manganin wire

Ohmic resistance

1. Resistance that follows Ohm's law is called Ohm resistance. For example, all-metal conductors (silver, aluminum, copper, iron, etc.)
2. Manganin is a brand name for copper-manganese-nickel alloys with an average composition of $84\%$ copper, $12\%$ manganese, and $4\%$ nickel. All these components are metal, thus, these obey Ohm's law.
3. Manganin foil and wire are used in the manufacture of resistors, especially ammeter shunts, due to their low-temperature coefficient and long service life.

Explanation for incorrect option(s):

(A) Diode valve

1. Made up of two conducting electrodes encased in a vacuum-tight glass envelope.
2. These are known as the cathode and anode, respectively.
3. Because of the energy generated from the heat, electrons are "boiled" off the electrodes when the cathode is heated.
4. This does not obey Ohm's law.

(B) Filament of a bulb

1. Filaments are components of a light bulb that produce light.
2. When an electric current is passed through the filament, the filament lights up.
3. In a vacuum tube, it is also called an electron emission element.
4. With the temperature the resistance of the filament changes, thus, this does not obeys Ohm's law.

(C) Carbon are light

1. Metal conductors are like carbon.
2. When large amounts of current flow through metal conductors, they heat up, and increase resistance, and the VI diagram deviates from Ohm's law.
3. It is classified as a non-Ohm conductor because it does not respect Ohm's law.

Thus, the ohmic resistance is manganin wire.

Hence, option D is the correct answer.