Lesson 4

Question 1

Here’s a comprehensive summary

Answer 1

clarification of key concepts

Question 2

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Question 3

Summary of Key Concepts

Question 4

• Galvanometer is an instrument used to detect and measure small electric currents

Answer 4

primarily indicated by the deflection of a magnetic needle or coil.

Question 5

• Historically

Answer 5

there are several types

Question 6

• Working Principle: When current passes through a coil in a magnetic field

Answer 6

it experiences a torque proportional to the current

Question 7

• The coil is suspended by a phosphor-bronze spring; the spring produces a counter-torque

Answer 7

balancing the magnetic torque at equilibrium.

Question 8

• Sensitivity measures the galvanometer’s ability to detect small currents and is proportional to the coil’s parameters and magnetic field.

Question 9

• Conversion Devices:

Question 10

o Ammeter: galvanometer with a shunt resistor in parallel.

Question 11

o Voltmeter: galvanometer with a high series resistor.

Question 12

• Applications: Detecting currents

Answer 12

measuring low currents and voltages

Question 13

• Advantages: High sensitivity

Answer 13

accuracy

Question 14

• Disadvantages: Only suitable for DC measurements

Answer 14

susceptible to aging

Question 15

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Question 16

Clarifications of Key Concepts

Question 17

• Magnetic Torque: A current-carrying coil experiences torque in a magnetic field

Answer 17

proportional to the current ((\tau = nIAB)). This causes the coil to rotate.

Question 18

• Deflection ((\theta)): The angle of coil deflection is directly proportional to the current ((\theta = \frac{nAB}{k}I))

Answer 18

where (k) is the torsional constant.

Question 19

• Sensitivity: The ratio of deflection to current

Answer 19

higher sensitivity means smaller currents cause noticeable deflections.

Question 20

• Conversion to Ammeter/Voltmeter:

Question 21

o Ammeter: Parallel shunt resistor reduces the total resistance for high currents.

Question 22

o Voltmeter: Series resistance limits current

Answer 22

measuring voltage across two points.

Question 23

• Effects of coil parameters: Increasing the number of turns

Answer 23

coil area

Question 24

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Question 25

Quiz Questions

Question 26

1. What is the primary purpose of a galvanometer?

Question 27

To detect and measure small electric currents.

Question 28

2. How does the coil experience torque in a moving coil galvanometer?

Question 29

By passing current through it in a magnetic field

Answer 29

creating a magnetic torque proportional to the current.

Question 30

3. What role does the phosphor-bronze spring play in the galvanometer?

Question 31

It provides a counter-torque that balances the magnetic torque

Answer 31

allowing the coil to come to a steady deflection.

Question 32

4. What is the main difference between a galvanometer used as an ammeter and as a voltmeter?

Question 33

An ammeter uses a shunt resistor in parallel to measure high currents

Answer 33

while a voltmeter uses a high series resistor to measure voltage.

Question 34

5. Name two factors that increase the sensitivity of a galvanometer.

Question 35

Number of turns in the coil and magnetic field strength.

Question 36

6. Why is a soft iron core used inside the galvanometer coil?

Question 37

To increase magnetic field strength and make the field radial

Answer 37

improving sensitivity.

Question 38

7. What is the physical principle behind the deflection in a galvanometer?

Question 39

The proportional relationship between the magnetic torque and the current passing through the coil.

Question 40

8. What is the key limitation of a moving coil galvanometer?

Question 41

It can only measure DC currents

Answer 41

not AC.

Question 42

9. How do you convert a galvanometer into a voltmeter?

Question 43

By connecting a high resistance in series with the galvanometer.

Question 44

10. What is the significance of the torsional constant (k)?

Question 45

It represents the restoring torque per unit twist of the suspension spring.

Question 46

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Question 47

Would you like more detailed explanations

Answer 47

additional questions