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Physics Core Concepts
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Physics Core Concepts
Physics Core Concepts
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1
Question
What is the SI unit of electric permittivity ε₀?
Answer
C² N⁻¹ m⁻² or C² / (N m²)
2
Question
What is the force acting on an alpha particle moving parallel to a magnetic field?
Answer
Zero
3
Question
For which color of light is the refractive index of glass minimum?
Answer
Red light
4
Question
Who proposed the first atomic model?
Answer
J. J. Thomson
5
Question
How does a semiconductor behave at 0 Kelvin?
Answer
Like an insulator
6
Question
How many electrons are there in one coulomb of charge?
Answer
6.25 × 10¹⁸ electrons
7
Question
What is the SI unit of capacitance?
Answer
Farad (F)
8
Question
What fields does a moving charge generate?
Answer
Both electric and magnetic fields
9
Question
Which substances have weak but positive magnetic susceptibility?
Answer
Paramagnetic substances
10
Question
What is the speed of electromagnetic waves in vacuum given by?
Answer
\( c = \frac{1}{\sqrt{\epsilon_0 \mu_0}} \)
11
Question
What is the approximate width of a PN junction diode?
Answer
10^{-6} m (or between 10^{-6} m and 10^{-7} m)
12
Question
What is the relationship between nuclear radius r and mass number A?
Answer
\( r = r_0 A^{1/3} \)
13
Question
What is the SI unit of current density?
Answer
Ampere per square meter (A/m²)
14
Question
What is the phase difference between current and voltage in a pure capacitor in an AC circuit?
Answer
π/2 radians, with current leading voltage
15
Question
In an atom, what happens to energy when the radius of an electron's orbit increases?
Answer
Energy increases
16
Question
In a reverse biased PN junction diode, which terminal is the N-type connected to?
Answer
Positive terminal of the battery
17
Question
What is the smallest possible charge?
Answer
Charge of an electron, 1.6 × 10^{-19} C
18
Question
What is the phase difference between current and voltage in a purely resistive AC circuit?
Answer
Zero
19
Question
What is the relationship between radius of curvature R and focal length f of a spherical mirror?
Answer
R = 2f
20
Question
What defines an ohmic resistor?
Answer
Obeys Ohm's law (e.g., copper wires)
21
Question
What is the CGS unit of magnetic field intensity?
Answer
Oersted or Gauss
22
Question
In a compound microscope, how does the focal length of the eyepiece compare to the objective?
Answer
Eyepiece has greater focal length than objective
23
Question
What is the electric potential at the midpoint between two equal and opposite point charges separated by distance 2a?
Answer
Zero
24
Question
What is the SI unit of magnetic flux?
Answer
Weber (Wb)
25
Question
What is the relationship between energy E and momentum p of a photon?
Answer
E = p c
26
Question
What is the path of an alpha particle scattered by a nucleus in Rutherford experiment?
Answer
Hyperbolic
27
Question
What is the effective length of a bar magnet compared to its actual length?
Answer
\( \frac{5}{6} \) of actual length
28
Question
Which rays remain undeflected in a magnetic field?
Answer
Gamma rays
29
Question
What is an electric cell a source of?
Answer
Electrical energy
30
Question
What is the direction of magnetic field at the center of a current-carrying circular coil?
Answer
Perpendicular to the plane of the coil