An electromagnet is made by MCQ with Answer and Explanation

An electromagnet is made by
A. Soft iron core
B. Steel core
C. Air core
D. Copper core
Answer: Option A
Solution (By JKExamLibrary)
Soft iron has high permeability, low retentivity, easily magnetized and demagnetized.

This question belongs to: Science Physics

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Practice More Physics Questions

Question #1 Report Error
In a p-n junction diode, the depletion region is created primarily due to:
A. Drift of electrons under a strong electric field.
B. Diffusion of majority charge carriers across the junction.
C. Heating of the semiconductor material.
D. Recombination of minority carriers.

Correct Answer: Option B


Explanation:
When a p-type and an n-type semiconductor are joined, electrons from the n-side (majority carriers) diffuse across the junction to the p-side, and holes from the p-side diffuse to the n-side due to concentration gradients. They recombine near the junction, leaving behind immobile ionized atoms (positive donor ions on n-side, negative acceptor ions on p-side). This uncovered charge region is the depletion layer.

This question belongs to: Science Physics
Question #2 Report Error
According to the Bohr model of the hydrogen atom, the total energy of an electron in the nth stationary orbit is directly proportional to:
A. n
B. 1 / n
C. 1 / n^2
D. n^2

Correct Answer: Option C


Explanation:
The total energy of an electron in a hydrogen-like atom in the nth orbit is strictly negative and given by the mathematical formula E_n = -13.6 Z^2 / n^2 (in eV). This formula demonstrates that the total energy is inversely proportional to the square of the principal quantum number (n^2).

This question belongs to: Science Physics
Question #3 Report Error
A car accelerates from rest at 2 m/s² for 10 s, then moves with constant velocity for 10 s. Total distance covered is
A. 200 m
B. 300 m
C. 100 m
D. 400 m

Correct Answer: Option B


Explanation:
Acceleration phase: s₁ = ½a t² = ½×2×100 = 100 m, v = a t = 20 m/s. Constant velocity phase: s₂ = v×t = 20×10 = 200 m. Total = 300 m. Motion in two parts.

This question belongs to: Science Physics