Practice MCQ Questions and answers on Physics-GK

Option B: Copper (Correct Answer)
Copper is an exception among common conductive materials. It has a negative temperature coefficient of resistance, meaning its resistance decreases as temperature increases. This unique property makes copper an excellent conductor of electricity and well-suited for applications where minimal resistance and efficient energy transmission are required.

Option A: Pure silicon
Silicon is a semiconductor material. In semiconductors like silicon, the resistance increases with an increase in temperature. This is due to the increased thermal generation of charge carriers (electrons and holes), which increases the conductivity and resistance.

Option C: Nichrome
Nichrome is a nickel-chromium alloy commonly used as a resistance wire in heating elements. It is known for its relatively high resistivity and stability at high temperatures. However, nichrome also exhibits a positive temperature coefficient of resistance, meaning its resistance increases with temperature.

Option D: Platinum
Platinum is a metal known for its excellent resistance to corrosion and high-temperature stability. However, like most metals, platinum exhibits a positive temperature coefficient of resistance. As temperature increases, the thermal vibrations of atoms within the metal lattice increase, causing greater scattering of electrons, which in turn increases resistance.

In summary, the other options (pure silicon, nichrome, and platinum) all have materials with a positive temperature coefficient of resistance, meaning their resistance increases as temperature rises. Copper, on the other hand, exhibits a negative temperature coefficient of resistance, making it the correct choice for a substance in which resistance decreases with increasing temperature.

Electric charge has the dimension electric current time. The SI derived unit of electric charge is the coulomb, which is defined as an ampere second.

It is directly proportional to the area of cross-section of wire is a false statement.

According to Ohm’s Law, the potential difference (V) between two terminals of a current-carrying conductor is directly proportional to the current (I), flowing through it. The proportionality constant R, is the resistance of the conductor. Thus, V α I
or V = I × R
or I = V/R
or R = V/I.

SI unit of electric current is Ampere.

The rate of flow of electric charge is measured in Ampere.

A fuse places a limit on the amount of current that can be drawn by an electric circuit by opening (blowing or melting) when the current exceeds a preset limit. This protects the circuit and the surroundings from fire or damage in the case of an overload or short circuit.

Materials that allow electricity to flow are called conductors.

The electrolyte consists of a solvent (water, an organic liquid, or even a solid) and one or more chemicals that dissociate into ions in the solvent. These ions serve to deliver electrons and chemical matter through the cell interior to balance the flow of electric current outside the cell during cell operation. An electrolyte is a liquid or gel that contains ions and can be decomposed by electrolysis, e.g., that present in a battery. Commonly, electrolytes are solutions of acids, bases, or salts. Electrolyte solutions can also result from the dissolution of some biological (e.g., DNA, polypeptides) and synthetic polymers (e.g., polystyrene sulfonate), termed poly-electrolytes, which contain charged functional groups.