Wheatstone Bridge | व्हीटस्टोन सेतु | Class 12 Physics

⚡ व्हीटस्टोन सेतु ⚡ Wheatstone Bridge

कक्षा 12 भौतिक विज्ञान | Complete Interactive Learning Class 12 Physics | Complete Interactive Learning

1. व्हीटस्टोन सेतु क्या है? 1. What is a Wheatstone Bridge?

व्हीटस्टोन सेतु एक विद्युत परिपथ है जिसका उपयोग अज्ञात प्रतिरोध (Unknown Resistance) का मान ज्ञात करने के लिए किया जाता है।

इसमें चार प्रतिरोधों को चार भुजाओं में जोड़ा जाता है और बीच में गैल्वेनोमीटर लगाया जाता है।

मुख्य बात: संतुलन की स्थिति में गैल्वेनोमीटर में धारा शून्य होती है।

A Wheatstone Bridge is an electrical circuit used to determine the value of an unknown resistance.

It consists of four resistances connected in four arms and a galvanometer connected between the junctions.

Key Point: When the bridge is balanced, the current through the galvanometer is zero.

2. व्हीटस्टोन सेतु का Animated Circuit 2. Animated Wheatstone Bridge Circuit

🔋 Battery

P

Q

R

S

G
Galvanometer

Key

🔴 लाल बिंदु विद्युत धारा के प्रवाह को दर्शाते हैं। 🔴 Red dots represent the flow of electric current.

3. परिपथ के मुख्य अवयव 3. Main Components of the Circuit

अवयव Component	कार्य Function
P, Q, R, S	चार प्रतिरोध Four resistances
G	गैल्वेनोमीटर Galvanometer
Battery	विद्युत ऊर्जा प्रदान करती है Provides electrical energy
Key	परिपथ को ON/OFF करती है Opens or closes the circuit

4. संतुलन की अवस्था 4. Balanced Condition

जब गैल्वेनोमीटर में धारा नहीं बहती है, तब Wheatstone Bridge संतुलित कहलाता है।

When no current flows through the galvanometer, the Wheatstone Bridge is said to be balanced.

P / Q = R / S

यदि S अज्ञात प्रतिरोध है:

If S is the unknown resistance:

S = QR / P

5. व्हीटस्टोन सेतु का सिद्धांत 5. Principle of Wheatstone Bridge

संतुलन की स्थिति में गैल्वेनोमीटर के दोनों सिरों का विभव समान होता है। इसलिए उनके बीच विभवांतर शून्य होता है।

At the balanced condition, the potentials at the two junctions connected to the galvanometer are equal. Therefore, the potential difference across the galvanometer is zero.

V_G = 0

I_G = 0

6. हल किया हुआ उदाहरण – 1 6. Solved Example – 1

एक Wheatstone Bridge में P = 2 Ω, Q = 4 Ω और R = 6 Ω है। Bridge संतुलित है। S ज्ञात कीजिए।

In a Wheatstone Bridge, P = 2 Ω, Q = 4 Ω and R = 6 Ω. The bridge is balanced. Find S.

Step 1 – Given / दिया गया:
P = 2 Ω
Q = 4 Ω
R = 6 Ω

Step 2 – Formula / सूत्र:

S = QR / P

Step 3 – Substitution / मान रखने पर:

S = (4 × 6) / 2

Step 4 – Calculation / गणना:

S = 24 / 2
S = 12 Ω

अंतिम उत्तर: S = 12 Ω Final Answer: S = 12 Ω

7. हल किया हुआ उदाहरण – 2 7. Solved Example – 2

P = 5 Ω, Q = 10 Ω और S = 20 Ω है। R ज्ञात कीजिए।

P = 5 Ω, Q = 10 Ω and S = 20 Ω. Find R.

P / Q = R / S

5 / 10 = R / 20

10R = 5 × 20

R = 10 Ω

अंतिम उत्तर: R = 10 Ω Final Answer: R = 10 Ω

8. हल किया हुआ उदाहरण – 3 8. Solved Example – 3

P = 3 Ω, Q = 6 Ω और R = 9 Ω है। S ज्ञात कीजिए।

P = 3 Ω, Q = 6 Ω and R = 9 Ω. Find S.

P / Q = R / S

3 / 6 = 9 / S

3S = 54

S = 18 Ω

अंतिम उत्तर: S = 18 Ω Final Answer: S = 18 Ω

9. महत्वपूर्ण सूत्र 9. Important Formulae

P / Q = R / S

S = QR / P

R = PS / Q

Q = PS / R

P = QR / S

10. Interactive Practice – प्रश्न 1 10. Interactive Practice – Question 1

P = 4 Ω, Q = 8 Ω और R = 6 Ω है। S ज्ञात कीजिए। P = 4 Ω, Q = 8 Ω and R = 6 Ω. Find S.

11. Interactive Practice – प्रश्न 2 11. Interactive Practice – Question 2

P = 5 Ω, Q = 10 Ω और S = 20 Ω है। R ज्ञात कीजिए। P = 5 Ω, Q = 10 Ω and S = 20 Ω. Find R.

12. Interactive Practice – प्रश्न 3 12. Interactive Practice – Question 3

P = 6 Ω, Q = 12 Ω और R = 15 Ω है। S ज्ञात कीजिए। P = 6 Ω, Q = 12 Ω and R = 15 Ω. Find S.

13. Interactive Practice – प्रश्न 4 13. Interactive Practice – Question 4

P = 2 Ω, Q = 5 Ω और S = 15 Ω है। R ज्ञात कीजिए। P = 2 Ω, Q = 5 Ω and S = 15 Ω. Find R.

14. Practice Set – स्वयं हल करें 14. Practice Set – Solve Yourself

1. P = 3 Ω, Q = 6 Ω, R = 12 Ω. S ज्ञात कीजिए।
2. P = 4 Ω, Q = 10 Ω, S = 20 Ω. R ज्ञात कीजिए।
3. P = 5 Ω, Q = 15 Ω, R = 10 Ω. S ज्ञात कीजिए।
4. P = 8 Ω, Q = 12 Ω, S = 18 Ω. R ज्ञात कीजिए।
5. P = 2 Ω, Q = 8 Ω, R = 10 Ω. S ज्ञात कीजिए।

1. P = 3 Ω, Q = 6 Ω, R = 12 Ω. Find S.
2. P = 4 Ω, Q = 10 Ω, S = 20 Ω. Find R.
3. P = 5 Ω, Q = 15 Ω, R = 10 Ω. Find S.
4. P = 8 Ω, Q = 12 Ω, S = 18 Ω. Find R.
5. P = 2 Ω, Q = 8 Ω, R = 10 Ω. Find S.

15. Quick Revision 15. Quick Revision

Wheatstone Bridge → अज्ञात प्रतिरोध ज्ञात करना

संतुलन की स्थिति:

P / Q = R / S

Galvanometer Current:

I_G = 0

Galvanometer Potential Difference:

V_G = 0

Wheatstone Bridge → Measurement of Unknown Resistance

Balanced Condition:

P / Q = R / S

Galvanometer Current:

I_G = 0

Potential Difference across Galvanometer:

V_G = 0

Class 12 Physics | व्हीटस्टोन सेतु
Concept • Animation • Solved Numericals • Practice Class 12 Physics | Wheatstone Bridge
Concept • Animation • Solved Numericals • Practice

Class XI Unit 3: - Classification of Elements and Periodicity in Properties,

Class XI Unit 3:

 Classification of Elements and Periodicity in Properties and the supplementary topics on s & p Block Elements,  competitive-level (JEE/NEET) 

Genesis & Modern Periodic Law

1. What is the physical basis of the Modern Periodic Law as proposed by Henry Moseley?
2. How does the Modern Periodic Law rectify the position of isotopes which was a drawback in Mendeleev’s table?
3. Why did the Law of Octaves fail to classify elements with higher atomic weights?
4. In the present form of the Periodic Table, the period number corresponds to which quantum number of the elements?
5. What is the significance of the atomic number being the fundamental property for classification instead of atomic mass?

Which element has the highest Electronegativity in the periodic table?

📚 Chapter: Classification of Elements and Periodicity in Properties

📘 Answer

🏆 Fluorine (F)

Fluorine (F) is the most electronegative element in the periodic table.

Its electronegativity on the Pauling scale is approximately 3.98, the highest value of all elements.

🔍 Why does Fluorine have the highest electronegativity?

• Fluorine has a very small atomic radius.
• It has a relatively high effective nuclear charge.
• Its valence shell is close to the nucleus.
• Therefore, it strongly attracts the shared electron pair in a chemical bond.

Small Atomic Radius + High Effective Nuclear Charge
↓
Strong Attraction for Shared Electrons
↓
Highest Electronegativity

📊 Important Comparison

Element	Approx. Pauling Electronegativity
F	3.98
O	3.44
Cl	3.16
N	3.04

✅ Final Answer

Fluorine (F)

Fluorine has the highest electronegativity in the periodic table, with a Pauling electronegativity of approximately 3.98.

20 MCQs with Answers

1. Which element has the highest electronegativity?

A) Oxygen

B) Chlorine

C) Fluorine

D) Nitrogen

✅ Answer

C) Fluorine

---

2. The electronegativity of fluorine on the Pauling scale is approximately:

A) 2.20

B) 3.00

C) 3.44

D) 3.98

✅ Answer

D) 3.98

---

3. Fluorine belongs to which group?

A) 1

B) 15

C) 17

D) 18

✅ Answer

C) 17

---

4. Fluorine has high electronegativity mainly because of:

A) Large atomic radius

B) Small atomic radius

C) Low nuclear charge

D) Many electron shells

✅ Answer

B) Small atomic radius

---

5. Which element is more electronegative than chlorine?

A) Fluorine

B) Bromine

C) Iodine

D) Sulfur

✅ Answer

A) Fluorine

---

6. Electronegativity generally increases:

A) Down a group

B) From right to left

C) From left to right across a period

D) Randomly

✅ Answer

C

---

7. Fluorine is a member of the:

A) Alkali metals

B) Alkaline earth metals

C) Halogens

D) Noble gases

✅ Answer

C) Halogens

---

8. Which property of fluorine contributes to its high electronegativity?

A) Small atomic size

B) Large number of shells

C) Low effective nuclear charge

D) Metallic character

✅ Answer

A) Small atomic size

---

9. Which has the greatest attraction for a shared electron pair?

A) Li

B) C

C) O

D) F

✅ Answer

D) F

---

10. The highest electronegativity is found toward the:

A) Bottom-left

B) Top-right

C) Centre

D) Bottom-centre

✅ Answer

B) Top-right

---

11. Which is the most electronegative halogen?

A) Cl

B) Br

C) I

D) F

✅ Answer

D) F

---

12. Which element has electronegativity approximately 3.44?

A) F

B) O

C) N

D) Cl

✅ Answer

B) O

---

13. The small atomic radius of fluorine results in:

A) Weak attraction for bonding electrons

B) Strong attraction for bonding electrons

C) Low electronegativity

D) High metallic character

✅ Answer

B

---

14. Fluorine has how many valence electrons?

A) 5

B) 6

C) 7

D) 8

✅ Answer

C) 7

---

15. Fluorine belongs to which block?

A) s-block

B) p-block

C) d-block

D) f-block

✅ Answer

B) p-block

---

16. Which element has higher electronegativity?

A) F

B) Cl

C) Both equal

D) I

✅ Answer

A) F

---

17. Electronegativity measures the ability of an atom to:

A) Attract shared electrons

B) Lose neutrons

C) Attract protons

D) Lose its nucleus

✅ Answer

A

---

18. Which element has the strongest non-metallic character among the following?

A) Na

B) Mg

C) Cl

D) K

✅ Answer

C) Cl

---

19. Fluorine's high electronegativity is associated with:

A) High effective nuclear charge

B) Very large atomic radius

C) Many occupied shells

D) Low nuclear attraction

✅ Answer

A

---

20. The correct statement is:

A) Fluorine has the lowest electronegativity

B) Fluorine has the highest electronegativity

C) Chlorine is more electronegative than fluorine

D) Electronegativity is absent in fluorine

✅ Answer

B) Fluorine has the highest electronegativity

Q. Which element has the highest electronegativity in the periodic table?

Solution: Fluorine (F) has the highest electronegativity in the periodic table. Its Pauling electronegativity is approximately 3.98.

Q. Why does fluorine have the highest electronegativity?

Solution:

• Fluorine has a very small atomic radius.
• It has a high effective nuclear charge.
• Therefore, it strongly attracts the shared electron pair towards itself.

Q. Explain the reasons for the highest electronegativity of fluorine.

Solution: Fluorine has the smallest atomic radius among the halogens and a high effective nuclear charge. Its valence electrons are close to the nucleus. Hence, the attraction between the nucleus and the shared pair of bonding electrons is very strong. Therefore, fluorine has the highest electronegativity, approximately 3.98 on the Pauling scale.

Q. Discuss the position of fluorine in the periodic trend of electronegativity.

Solution:

Electronegativity generally increases from left to right across a period and decreases down a group. Fluorine is located in Group 17 and Period 2. It has a very small atomic size and high effective nuclear charge.

Because its valence shell is very close to the nucleus, fluorine strongly attracts the shared pair of electrons in a covalent bond. Hence, it has the highest electronegativity of all elements.

Fluorine (F) → Highest Electronegativity → ≈ 3.98 (Pauling scale)

Q. Explain in detail why fluorine has the highest electronegativity in the periodic table.

1. Small Atomic Size

Fluorine is a second-period element and has only two occupied electron shells. Its atomic radius is therefore very small.

2. High Effective Nuclear Charge

Fluorine has nine protons, while its inner-shell electrons provide relatively limited shielding. Thus its valence electrons experience a strong effective nuclear attraction.

3. Strong Attraction for Bonding Electrons

Because the valence shell is close to the nucleus, fluorine strongly attracts the shared electron pair in a covalent bond.

4. Periodic Trend

Electronegativity generally increases across a period and decreases down a group. Fluorine is at the upper-right side of the periodic table (excluding noble gases), where electronegativity is highest.

Small Atomic Radius
+
High Effective Nuclear Charge
↓
Strong Attraction for Shared Electrons
↓
Highest Electronegativity: F

Final Answer:
Fluorine (F) is the most electronegative element in the periodic table. Its Pauling electronegativity is approximately 3.98.

🎯 Quick Revision

Highest Electronegativity: Fluorine (F)
Group: 17
Period: 2
Block: p-block
Pauling value: ≈ 3.98
Main reason: Small atomic radius + high effective nuclear charge