IIT JEE Physics Practice Paper – Nuclei & Semiconductor (Set 15)

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1. Mass defect is:

Difference between nucleon mass and nucleus mass
Total mass
Binding energy
None

2. Binding energy is:

Energy required to break nucleus
Energy to move electron
Energy of photon
None

3. Relation between mass and energy:

\(E = mc^2\)
\(V = IR\)
\(F = ma\)
None

4. Half-life is time when nuclei become:

Half
Double
Zero
None

5. Decay law:

\(N = N_0 e^{-\lambda t}\)
\(V=IR\)
\(F=ma\)
None

6. Unit of radioactivity:

Becquerel
Joule
Watt
None

7. Alpha particle is:

Helium nucleus
Electron
Proton
None

8. Beta decay emits:

Electron
Proton
Neutron
None

9. Gamma rays are:

Electromagnetic waves
Particles
Neutrons
None

10. Nuclear force is:

Strong
Weak
Electric
None

11. Semiconductor has:

Moderate conductivity
High
Zero
None

12. Intrinsic semiconductor is:

Pure
Doped
Conductor
None

13. Extrinsic semiconductor is:

Doped
Pure
Insulator
None

14. n-type semiconductor has:

Electrons
Holes
Protons
None

15. p-type semiconductor has:

Holes
Electrons
Neutrons
None

16. Diode conducts in:

Forward bias
Reverse bias
Both
None

17. Reverse current is:

Small
Large
Zero
None

18. Zener diode is used for:

Voltage regulation
Amplification
Cooling
None

19. AND gate output is 1 when:

Both inputs 1
Any input 1
Both 0
None

20. OR gate output is 1 when:

Any input 1
Both 0
None
Zero

21. NOT gate is:

Inverter
Amplifier
Resistor
None

22. Common semiconductor material:

Silicon
Copper
Iron
None

23. Doping increases:

Conductivity
Resistance
Mass
None

24. PN junction forms:

Depletion region
Conductor
Insulator
None

25. Barrier potential exists in:

PN junction
Metal
Wire
None

26. LED emits:

Light
Heat
Sound
None

27. Transistor is used for:

Amplification
Cooling
Heating
None

28. Collector current is:

Largest
Smallest
Equal
None

29. Semiconductor band gap is:

Small
Large
Zero
None

30. Conductivity increases with:

Temperature
Pressure
Volume
None

Submit

IIT JEE Physics Practice Paper – Nuclei & Semiconductor (Set 15) Notes

Nuclei

Atomic Structure Basics

• Nucleus contains protons and neutrons
• Atomic number $Z$Z = number of protons
• Mass number $A$A = protons + neutrons

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Mass Defect

Definition

Difference between total mass of nucleons and actual nuclear mass

Formula

$$\Delta m = (\text{sum of masses}) – (\text{actual mass})$$Δm=(sum of masses)−(actual mass)

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Binding Energy

Concept

Energy required to break nucleus into individual nucleons

Formula

$$E = \Delta m \, c^2$$E=Δmc2

Key Insight

Higher binding energy → more stable nucleus

---

Binding Energy Curve

Observations

• Maximum at iron (Fe)
• Light nuclei → fusion
• Heavy nuclei → fission

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Radioactive Decay Law

Formula

$$N = N_0 e^{-\lambda t}$$N=N0​e−λt

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Half-Life

Definition

Time required for quantity to reduce to half

Formula

$$T_{1/2} = \frac{\ln 2}{\lambda}$$T1/2​=λln2​

---

Activity of Radioactive Substance

Formula

$$A = \lambda N$$A=λN

Unit

• Becquerel (Bq)

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Types of Radioactive Decay

Alpha Decay

• Emits helium nucleus
• Mass decreases by 4

Beta Decay

• Emits electron
• Neutron → proton

Gamma Decay

• Emits electromagnetic radiation
• No change in mass or charge

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Nuclear Force

Properties

• Very strong
• Short range
• Independent of charge

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Nuclear Energy

Fission

• Heavy nucleus splits into smaller nuclei

Fusion

• Light nuclei combine to form heavier nucleus

---

Semiconductors

Definition

Materials with conductivity between conductors and insulators

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Intrinsic Semiconductor

Concept

• Pure semiconductor
• Equal electrons and holes

---

Extrinsic Semiconductor

Concept

Doped semiconductor

Types

• n-type → electrons majority
• p-type → holes majority

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PN Junction

Formation

Joining p-type and n-type materials

Depletion Region

Region without free charge carriers

---

Barrier Potential

Definition

Potential difference across PN junction preventing current flow

---

Biasing of Diode

Forward Bias

• Allows current flow

Reverse Bias

• Blocks current (very small leakage)

---

Zener Diode

Function

Used for voltage regulation

---

LED (Light Emitting Diode)

Working

Emits light when forward biased

---

Transistor

Uses

• Amplification
• Switching

Relation

$$I_E = I_B + I_C$$IE​=IB​+IC​

---

Logic Gates

AND Gate

Output = 1 only if both inputs = 1

OR Gate

Output = 1 if any input = 1

NOT Gate

Output is opposite of input

---

Band Theory

Semiconductors

• Small band gap

Temperature Effect

• Conductivity increases with temperature

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Important Formulas

Mass-Energy Relation

$$E = mc^2$$E=mc2

Decay Law

$$N = N_0 e^{-\lambda t}$$N=N0​e−λt

Half-Life

$$T_{1/2} = \frac{\ln 2}{\lambda}$$T1/2​=λln2​

Activity

$$A = \lambda N$$A=λN

---

Common Mistakes

Concept Errors

• Confusing decay types
• Mixing n-type and p-type

Formula Errors

• Forgetting exponential decay
• Misusing half-life formula

---

Quick Revision Tips

Nuclei

• Binding energy → stability
• Decay is exponential

Semiconductor

• Diode works in forward bias
• Doping increases conductivity

---

Conclusion

Focus Areas

• Radioactive decay formulas
• Nuclear reactions
• PN junction behavior
• Logic gates

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