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Q.11 Medium Physics
A 1000 W heater operates at 250 V. What is its resistance?
A 0.25 Ω
B 4 Ω
C 62.5 Ω
D 250000 Ω
Correct Answer:  C. 62.5 Ω
EXPLANATION

Using P = V²/R, we get R = V²/P = (250)²/1000 = 62500/1000 = 62.5 Ω.

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Q.12 Medium Physics
Which phenomenon explains the blue color of the sky?
A Total internal reflection
B Rayleigh scattering
C Mie scattering
D Interference
Correct Answer:  B. Rayleigh scattering
EXPLANATION

Rayleigh scattering causes shorter blue wavelengths to scatter more effectively than longer red wavelengths when sunlight passes through the atmosphere, making the sky appear blue.

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Q.13 Medium Physics
A nucleus undergoes beta decay. Which particle is emitted along with an antineutrino?
A Alpha particle
B Electron
C Neutron
D Photon
Correct Answer:  B. Electron
EXPLANATION

In beta-minus decay, a neutron converts to a proton, emitting an electron (beta particle) and an antineutrino. This increases atomic number by 1.

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Q.14 Medium Physics
Which statement about alpha decay is correct?
A An alpha particle is a helium nucleus with 2 protons and 2 neutrons
B Alpha decay increases the atomic number
C Alpha particles have high penetration power
D Alpha decay produces beta particles
Correct Answer:  A. An alpha particle is a helium nucleus with 2 protons and 2 neutrons
EXPLANATION

An alpha particle is a helium-4 nucleus (₂He⁴) with 2 protons and 2 neutrons. Alpha decay decreases atomic number by 2 and mass number by 4. Alpha particles have low penetration power.

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Q.15 Medium Physics
A transformer has 100 turns in the primary coil and 500 turns in the secondary coil. If the primary voltage is 220V, what is the secondary voltage assuming 100% efficiency?
A 44 V
B 220 V
C 1100 V
D 2200 V
Correct Answer:  C. 1100 V
EXPLANATION

Using transformer equation: Vₛ/Vₚ = Nₛ/Nₚ. Vₛ = 220 × (500/100) = 220 × 5 = 1100 V.

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Q.16 Medium Physics
What is the SI unit of magnetic flux?
A Tesla
B Weber
C Gauss
D Henry
Correct Answer:  B. Weber
EXPLANATION

The Weber (Wb) is the SI unit of magnetic flux, defined as Tesla × meter². 1 Wb = 1 T·m².

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Q.17 Medium Physics
Which of the following is a non-ohmic conductor?
A Copper wire at constant temperature
B Tungsten filament in a light bulb
C Nichrome wire at constant temperature
D Silver wire at constant temperature
Correct Answer:  B. Tungsten filament in a light bulb
EXPLANATION

A tungsten filament's resistance changes significantly with temperature during operation, making it non-ohmic. Metals at constant temperature follow Ohm's law.

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Q.18 Medium Physics
Two resistors of 4Ω and 6Ω are connected in series with a 10V battery. What is the total current?
A 1 A
B 2 A
C 10/6 A
D 10/4 A
Correct Answer:  A. 1 A
EXPLANATION

Total resistance = 4 + 6 = 10Ω. Using Ohm's law: I = V/R = 10/10 = 1 A.

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Q.19 Medium Physics
A light ray travels from air (n=1) into glass (n=1.5) at an incident angle of 30°. What is the refraction angle?
A 15°
B 19.47°
C 22.08°
D 30°
Correct Answer:  B. 19.47°
EXPLANATION

Using Snell's Law: n₁sinθ₁ = n₂sinθ₂. 1 × sin(30°) = 1.5 × sinθ₂. 0.5 = 1.5sinθ₂. sinθ₂ = 0.333. θ₂ ≈ 19.47°.

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Q.20 Medium Physics
Which phenomenon occurs when sound waves bend around obstacles?
A Reflection
B Refraction
C Diffraction
D Interference
Correct Answer:  C. Diffraction
EXPLANATION

Diffraction is the bending of waves around obstacles or through openings. This explains why we can hear sounds around corners.

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