Physics and Measurement Notes for NEET Exam
1. Units of Measurements
Definition: A unit is a standard quantity used to measure physical quantities.
Importance: Ensures uniformity and consistency in measurements.
Types of Units:
- Fundamental Units: Basic units like meter, kilogram, second.
- Derived Units: Combinations of fundamental units like Newton, Joule.
NEET PYQ 2021: Which of the following is a fundamental unit?
A) Joule
B) Pascal
C) Second
D) Watt
Answer: C) Second
Explanation: Second is a fundamental unit of time, while Joule, Pascal, and Watt are derived units.
NEET PYQ 2019: Which of the following is not a fundamental unit?
A) Ampere
B) Kelvin
C) Mole
D) Newton
Answer: D) Newton
Explanation: Newton is a derived unit, as it is defined as kg·m/s². Fundamental units are basic and cannot be expressed in terms of other units.
NEET PYQ 2017: Which of the following is a fundamental unit in the SI system?
A) Joule
B) Pascal
C) Second
D) Watt
Answer: C) Second
Explanation: Second is a fundamental unit of time in the SI system, while Joule, Pascal, and Watt are derived units.
NEET PYQ 2015: Which of the following is a derived unit?
A) Meter
B) Kilogram
C) Newton
D) Second
Answer: C) Newton
Explanation: Newton is a derived unit, defined as kg·m/s², while meter, kilogram, and second are fundamental units.
2. System of Units
CGS System: Centimeter, Gram, Second.
MKS System: Meter, Kilogram, Second.
FPS System: Foot, Pound, Second.
SI System: International System of Units, most widely used.
NEET PYQ 2021: The SI unit of luminous intensity is:
A) Candela
B) Lux
C) Lumen
D) Watt
Answer: A) Candela
Explanation: Candela is the SI unit of luminous intensity.
NEET PYQ 2018: The SI unit of luminous intensity is:
A) Candela
B) Lux
C) Lumen
D) Watt
Answer: A) Candela
Explanation: Candela is the SI unit of luminous intensity, which measures the power emitted by a light source in a particular direction.
NEET PYQ 2016: Which system of units is based on centimeter, gram, and second?
A) MKS
B) CGS
C) FPS
D) SI
Answer: B) CGS
Explanation: The CGS system is based on centimeter (length), gram (mass), and second (time).
NEET PYQ 2014: The SI system is an extension of which system?
A) CGS
B) MKS
C) FPS
D) None of the above
Answer: B) MKS
Explanation: The SI system is an extension of the MKS (Meter-Kilogram-Second) system.
3. SI Units
Base Units: Meter (m), Kilogram (kg), Second (s), Ampere (A), Kelvin (K), Mole (mol), Candela (cd).
Derived Units: Newton (N), Joule (J), Pascal (Pa), Watt (W).
NEET PYQ 2022: The SI unit of electric charge is:
A) Coulomb
B) Ampere
C) Volt
D) Ohm
Answer: A) Coulomb
Explanation: Coulomb is the SI unit of electric charge.
NEET PYQ 2017: The SI unit of electric charge is:
A) Coulomb
B) Ampere
C) Volt
D) Ohm
Answer: A) Coulomb
Explanation: Coulomb is the SI unit of electric charge, defined as the charge transported by a constant current of one ampere in one second.
NEET PYQ 2015: The SI unit of force is:
A) Joule
B) Newton
C) Pascal
D) Watt
Answer: B) Newton
Explanation: Newton is the SI unit of force, defined as kg·m/s².
NEET PYQ 2013: The SI unit of power is:
A) Joule
B) Newton
C) Watt
D) Pascal
Answer: C) Watt
Explanation: Watt is the SI unit of power, defined as one joule per second.
4. Fundamental and Derived Units
Fundamental Units: Independent units like meter, kilogram, second.
Derived Units: Dependent on fundamental units like Newton (kg·m/s²).
NEET PYQ 2016: Which of the following is a derived unit?
A) Meter
B) Kilogram
C) Second
D) Newton
Answer: D) Newton
Explanation: Newton is a derived unit, as it is defined in terms of fundamental units (kg·m/s²).
NEET PYQ 2014: Which of the following is a fundamental unit?
A) Joule
B) Pascal
C) Second
D) Watt
Answer: C) Second
Explanation: Second is a fundamental unit of time, while Joule, Pascal, and Watt are derived units.
NEET PYQ 2012: Which of the following is a derived unit?
A) Ampere
B) Kelvin
C) Mole
D) Pascal
Answer: D) Pascal
Explanation: Pascal is a derived unit of pressure, defined as N/m² or kg·m⁻¹·s⁻².
5. Least Count
Definition: The smallest measurement that can be taken by a measuring instrument.
Example: Least count of a vernier caliper is 0.01 cm.
NEET PYQ 2022: The least count of a screw gauge is:
A) 0.01 mm
B) 0.1 mm
C) 1 mm
D) 0.001 mm
Answer: A) 0.01 mm
Explanation: The least count of a screw gauge is typically 0.01 mm.
NEET PYQ 2015: The least count of a screw gauge is:
A) 0.01 mm
B) 0.1 mm
C) 1 mm
D) 0.001 mm
Answer: A) 0.01 mm
Explanation: The least count of a screw gauge is calculated as the pitch divided by the number of divisions on the circular scale. For most screw gauges, it is 0.01 mm.
NEET PYQ 2013: The least count of a vernier caliper is:
A) 0.01 cm
B) 0.1 cm
C) 0.001 cm
D) 0.02 cm
Answer: A) 0.01 cm
Explanation: The least count of a vernier caliper is typically 0.01 cm, calculated as 1 main scale division (1 mm) minus 1 vernier scale division (0.9 mm).
NEET PYQ 2011: The least count of a micrometer screw gauge is:
A) 0.01 mm
B) 0.1 mm
C) 0.001 mm
D) 0.0001 mm
Answer: A) 0.01 mm
Explanation: The least count of a micrometer screw gauge is 0.01 mm, calculated as the pitch (0.5 mm) divided by the number of divisions on the circular scale (50).
6. Significant Figures
Definition: The number of meaningful digits in a measured quantity.
Rules:
- All non-zero digits are significant.
- Zeros between non-zero digits are significant.
- Leading zeros are not significant.
- Trailing zeros are significant if there is a decimal point.
NEET PYQ 2023: How many significant figures are in 0.00420?
A) 2
B) 3
C) 4
D) 5
Answer: B) 3
Explanation: Leading zeros are not significant. Only the digits 4, 2, and the trailing zero after the decimal are significant.
NEET PYQ 2014: How many significant figures are in 0.0025?
A) 1
B) 2
C) 3
D) 4
Answer: B) 2
Explanation: Leading zeros are not significant. Only the digits 2 and 5 are significant in 0.0025.
NEET PYQ 2012: How many significant figures are in 100.00?
A) 2
B) 3
C) 4
D) 5
Answer: D) 5
Explanation: Trailing zeros after a decimal point are significant. Therefore, 100.00 has 5 significant figures.
NEET PYQ 2010: How many significant figures are in 0.00420?
A) 2
B) 3
C) 4
D) 5
Answer: B) 3
Explanation: Leading zeros are not significant. Only the digits 4, 2, and the trailing zero after the decimal are significant in 0.00420.
7. Errors in Measurements
Types of Errors:
- Systematic Errors: Consistent, predictable errors.
- Random Errors: Unpredictable, vary with each measurement.
- Gross Errors: Due to carelessness or faulty equipment.
Minimization: Calibration, repeated measurements.
NEET PYQ 2023: Which of the following is a systematic error?
A) Parallax error
B) Human error
C) Instrumental error
D) All of the above
Answer: C) Instrumental error
Explanation: Instrumental error is a systematic error caused by faulty calibration or defects in the measuring instrument.
NEET PYQ 2013: Which of the following is a systematic error?
A) Parallax error
B) Human error
C) Instrumental error
D) All of the above
Answer: C) Instrumental error
Explanation: Instrumental error is a systematic error as it arises due to faulty calibration or defects in the measuring instrument.
NEET PYQ 2011: Which of the following is a random error?
A) Zero error in a screw gauge
B) Human error in reading a scale
C) Error due to temperature fluctuations
D) Error due to incorrect calibration
Answer: C) Error due to temperature fluctuations
Explanation: Random errors are unpredictable and arise due to external factors like temperature fluctuations.
NEET PYQ 2009: Gross errors in measurements are caused by:
A) Carelessness
B) Faulty equipment
C) Both A and B
D) None of the above
Answer: C) Both A and B
Explanation: Gross errors are caused by carelessness or faulty equipment.
8. Dimensions of Physical Quantities
Definition: The powers to which the fundamental units are raised to represent a physical quantity.
Example: Force has dimensions [M L T⁻²].
NEET PYQ 2024: The dimensional formula for pressure is:
A) [M L⁻¹ T⁻²]
B) [M L T⁻²]
C) [M L² T⁻²]
D) [M L⁻² T⁻²]
Answer: A) [M L⁻¹ T⁻²]
Explanation: Pressure is defined as force per unit area. Force has dimensions [M L T⁻²], and area has dimensions [L²]. Therefore, pressure has dimensions [M L⁻¹ T⁻²].
NEET PYQ 2012: The dimensional formula for energy is:
A) [M L² T⁻²]
B) [M L T⁻²]
C) [M L² T⁻¹]
D) [M L T⁻¹]
Answer: A) [M L² T⁻²]
Explanation: Energy (work) is defined as force × distance. Force has dimensions [M L T⁻²], and distance has dimensions [L]. Therefore, energy has dimensions [M L² T⁻²].
NEET PYQ 2010: The dimensional formula for pressure is:
A) [M L⁻¹ T⁻²]
B) [M L T⁻²]
C) [M L² T⁻²]
D) [M L⁻² T⁻²]
Answer: A) [M L⁻¹ T⁻²]
Explanation: Pressure is defined as force per unit area. Force has dimensions [M L T⁻²], and area has dimensions [L²]. Therefore, pressure has dimensions [M L⁻¹ T⁻²].
NEET PYQ 2008: The dimensional formula for power is:
A) [M L² T⁻³]
B) [M L T⁻²]
C) [M L² T⁻²]
D) [M L⁻² T⁻²]
Answer: A) [M L² T⁻³]
Explanation: Power is defined as energy per unit time. Energy has dimensions [M L² T⁻²], and time has dimensions [T]. Therefore, power has dimensions [M L² T⁻³].
9. Dimensional Analysis and Its Applications
Dimensional Analysis: A method to check the correctness of equations.
Applications:
- Deriving relationships between physical quantities.
- Converting units from one system to another.
- Checking the consistency of equations.
NEET PYQ 2024: The dimensional formula for energy is:
A) [M L² T⁻²]
B) [M L T⁻²]
C) [M L² T⁻¹]
D) [M L T⁻¹]
Answer: A) [M L² T⁻²]
Explanation: Energy (work) is defined as force × distance. Force has dimensions [M L T⁻²], and distance has dimensions [L]. Therefore, energy has dimensions [M L² T⁻²].
NEET PYQ 2011: The dimensional formula for gravitational constant (G) is:
A) [M⁻¹ L³ T⁻²]
B) [M L² T⁻²]
C) [M L T⁻²]
D) [M L⁻² T⁻²]
Answer: A) [M⁻¹ L³ T⁻²]
Explanation: The gravitational constant (G) is given by the equation \( F = \frac{G m_1 m_2}{r^2} \). Solving for G, we get \( G = \frac{F r^2}{m_1 m_2} \), which has dimensions [M⁻¹ L³ T⁻²].
NEET PYQ 2009: The dimensional formula for Planck's constant (h) is:
A) [M L² T⁻¹]
B) [M L T⁻²]
C) [M L² T⁻²]
D) [M L⁻² T⁻²]
Answer: A) [M L² T⁻¹]
Explanation: Planck's constant (h) is given by the equation \( E = h \nu \), where \( \nu \) is frequency. Therefore, \( h = \frac{E}{\nu} \), which has dimensions [M L² T⁻¹].
NEET PYQ 2007: The dimensional formula for angular momentum is:
A) [M L² T⁻¹]
B) [M L T⁻²]
C) [M L² T⁻²]
D) [M L⁻² T⁻²]
Answer: A) [M L² T⁻¹]
Explanation: Angular momentum (L) is given by \( L = r \times p \), where \( r \) is distance and \( p \) is momentum. Therefore, \( L \) has dimensions [M L² T⁻¹].
