A magnetic dipole in a constant magnetic field has
1
zero potential energy when the torque is maximum
2
minimum potential energy when the torque is maximum
3
maximum potential energy when the torque is maximum
4
zero potential energy when the torque is minimum
Official Solution
Correct Option:
(1)
Step 1: Torque on a magnetic dipole in a magnetic field is
where is the angle between and . Step 2: Torque is maximum when
Step 3: Potential energy of a magnetic dipole in a magnetic field is
Step 4: At ,
Step 5: Hence, when the torque is maximum, the potential energy is zero.
02
PYQ 2022
medium
physicsID: lpunest-
A proton accelerated by a potential difference moves through a transverse magnetic field as shown in the figure. The width of the magnetic field region is . Then the angle through which the proton deviates from the initial direction of its motion is (approximately)
1
2
3
4
Official Solution
Correct Option:
(2)
Step 1: Find the speed of the proton after acceleration through potential .
For a proton:
Step 2: Radius of circular path in magnetic field:
Step 3: The proton travels an arc of a circle inside the field. From geometry (see figure),
Here,
03
PYQ 2024
medium
physicsID: lpunest-
Find equivalent capacitance between points A and B. Assume each conducting plate has same dimensions and neglect the thickness of plate. It is given that
where A is the area of plates.
1
7 \mu F
2
11 \mu F
3
12 \mu F
4
15 \mu F
Official Solution
Correct Option:
(3)
Step 1: From the figure, there are three capacitors formed by six plates. For plates of equal area, capacitances are proportional to . Step 2: Using the given reference:
Step 3: The three gaps in the diagram are . Therefore individual capacitances:
Step 4: These are in parallel between A and B:
Hence → (C).
04
PYQ 2024
medium
physicsID: lpunest-
When an electric heater is switched on, the current is plotted against time . Taking into account the variation of resistance with temperature, which of the following best represents the resulting curve?
1
continuously decreasing curve
2
straight line rise
3
curve bending downward
4
curve bending upward
Official Solution
Correct Option:
(1)
Step 1: For heater, temperature increases with time. Step 2: Metallic resistance increases with temperature:
Step 3: Therefore current gradually decreases, not increases. Step 4: Option (A) showing decreasing current is correct.
05
PYQ 2025
medium
physicsID: lpunest-
Which of the following temperatures is the highest?
1
2
3
4
Official Solution
Correct Option:
(2)
Step 1: Convert all temperatures to the same scale (Celsius). Step 2: Convert to Celsius.
Step 3: Convert to Celsius.
Step 4: Write the remaining values in Celsius. Step 5: Compare all temperatures in Celsius. The highest temperature (closest to zero) is:
But among the converted values:
Comparing all options correctly:
However, option (B) corresponds to , which is lower than . Thus, re-check: Highest = Final Answer:
06
PYQ 2025
medium
physicsID: lpunest-
Which of the following pairs may give equal numerical values of the temperature of human body?
1
Fahrenheit and Celsius
2
Celsius and Kelvin
3
Kelvin and Reaumur
4
None of these
Official Solution
Correct Option:
(4)
Step 1: Recall the normal temperature of the human body. Normal human body temperature is approximately:
Step 2: Check equality of numerical values between different scales.
Fahrenheit and Celsius: They are numerically equal only at , not at body temperature.
Celsius and Kelvin:
So numerical equality is impossible.
Kelvin and Reaumur:
No numerical equality occurs at body temperature.
Step 3: Final conclusion. None of the given pairs have equal numerical values for the temperature of the human body.
About Electrostatics - LPUNEST
Electrostatics is a vital chapter for LPUNEST aspirants. Mastering the concepts covered in this chapter is essential for securing a top rank.
By rigorously practicing the previous year questions associated with this chapter, you can identify high-yield topics, understand the examiner's perspective, and boost your confidence during the actual exam.
Frequently Asked Questions
Why focus on Electrostatics PYQs?
Analyzing PYQs for this specific chapter reveals the most frequently tested concepts and the typical complexity of questions, allowing you to tailor your study plan efficiently.
How to best use this analysis?
Review the topic breakdown to see which sub-topics within Electrostatics carry the most weight. Then, tackle the questions iteratively to solidify your understanding.