In Class 12 Boards there will be Case studies and Passage Based Questions will be asked, So practice these types of questions. Study Rate is always there to help you. Free PDF Download of CBSE Class 12 Physics Chapter 1 Electric Charges and Fields Case Study and Passage-Based Questions with Answers were Prepared Based on Latest Exam Pattern. Students can solve NCERT Class 12 Physics Case Study Questions  Electric Charges and Fields to know their preparation level.
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In CBSE Class 12 Physics Paper, Students will have to answer some questions based on Assertion and Reason. There will be a few questions based on case studies and passage-based as well. In that, a paragraph will be given, and then the MCQ questions based on it will be asked.
Electric Charges and Fields Case Study Questions With Answers
Here, we have provided case-based/passage-based questions for Class 12 Physics Chapter 1 Electric Charges and Fields
Case Study/Passage-Based Questions
Case Study 1: In 1909, Robert Millikan was the first to find the charge of an electron in his now-famous oil-drop experiment. In that experiment, tiny oil drops were sprayed into a uniform electric field between a horizontal pair of oppositely charged plates. The drops were observed with a magnifying eyepiece, and the electric field was adjusted so that the upward force on some negatively charged oil drops was just sufficient to balance the downward force of gravity. That is, when suspended, upward force qE just equaled Mg. Millikan accurately measured the charges on many oil drops and found the values to be whole number multiples of 1.6 x 10-19Â C the charge of the electron. For this, he won the Nobel prize.
(i) If a drop of mass 1.08 x 10-14Â kg remains stationary in an electric field of 1.68 x 105Â N C-I, then the charge of this drop is
| (a) 6.40 x 10-19 C | (b) 3.2 x 10-19 C |
| (c) 1.6 X 10-19 C | (d) 4.8 x 10-19 C |
Answer: (a) 6.40 x 10-19Â C
(ii) Extra electrons on this particular oil drop (given the presently known charge of the electron) are
| (a) 4 | (b) 3 | (c) 5 | (d) 8 |
Answer: (a) 4
(iii) A negatively charged oil drop is prevented from falling under gravity by applying a vertical electric field 100 V m-1.If the mass of the drop is 1.6 X 10-3 g, the number of electrons carried by the drop is (g= 10 m s-2)
| (a) 1018 | (b) 1015 | (c) 1012 | (d) 109 |
Answer: (c) 1012 .
(iv) The important conclusion given by Millikan’s experiment about the charge is
| (a) charge is never quantized | (b) charge has no definite value |
| (c) charge is quantized | (d) charge on oil drop always increases. |
Answer: (c) charge is quantized
(v) If in Millikan’s oil drop experiment, charges on drops are found to be 8μC,12μC,20μC8μC,12μC,20μC then quanta of charge is
| (a) 8μC | (b) 20μC | (c) 12μC | (d) 4μC |
Answer:  (d) 4μC
Case Study 2: Surface Charge Density. Surface charge density is defined as the charge per unit surface area the surface (Arial) charge symmetric distribution and follow Gauss law of electrostatics mathematical term of surface charge density σ=ΔQ/ΔS
Two large thin metal plates are parallel and close to each other. On their inner faces, the plates have surface charge densities of opposite sign (± s). Having magnitude 8.8 × 10–12 cm–2 as shown here. The intensity of electrified at a point is E =σ/ε0 and flux is Φ=E.ΔS, where ΔS = 1 m2 (unit arial plate)
(i) E in the outer region (I) of the first (A) plate is
(a) 1.7 × 10–22 N/C
(b) 1.1 × 10–12 V/m
(c) Zero
(d) Insufficient data
Ans. (c) Zero C
(ii) E in the outer region (III) of the second plate (B) is
(a) 1 N/C
(b) 0.1 V/m
(c) 0.5 N/C
(d) zero
Ans. (d) Zero
(iii) E between (II) the plate is
(a) 1 N/C
(b) 0.1 V/m
(c) 0.5 N/C
(d) None of these
Ans. (d) None of these
(iv) The ratio of E from left side of plate A at distance 1 cm and 2 m respectively is
(a) 1 : 2
(b) 10 : 2
(c) 1 : 1
(d) 20 : 1
Ans. (c) 1 : 1
(v) In order to estimate the electric field due to a thin finite plane metal plate the Gaussian surface considered is
(a) Spherical
(b) Linear
(c) Cylindrical
(d) Cybic
Ans. (c) Cylindrical
Case Study 3: Electric Charges and Fields, focuses on the basic properties of electric charges, the concept of electric fields, and the forces acting within these fields. The chapter introduces the idea that like charges repel, and unlike charges attract, a fundamental law of electrostatics. It also discusses the principle of superposition, which states that the net electrostatic force experienced by a charge due to multiple charges is simply the vector sum of the individual forces exerted by each charge independently. Further, the chapter introduces the concept of an electric field, defined as the electric force experienced by a unit positive charge at a point in space, and illustrates the way these fields are represented using field lines.
What is the basic property of electric charges?
A) Like charges repel, and unlike charges attract.
B) Like charges attract, and unlike charges repel.
C) All charges repel.
D) All charges attract.
Ans. A) Like charges repel, and unlike charges attract.
What does the principle of superposition state in terms of electrostatic forces?
A) The net electrostatic force is equal to the sum of the individual forces.
B) The net electrostatic force is equal to the difference of the individual forces.
C) The net electrostatic force is independent of the individual forces.
D) The net electrostatic force is inversely proportional to the individual forces.
Ans. A) The net electrostatic force is equal to the sum of the individual forces.
What is an electric field?
A) The region around a charge where magnetic force is experienced.
B) The region around a charge where gravitational force is experienced.
C) The region around a charge where electrostatic force is experienced.
D) The region around a charge where nuclear force is experienced.
Ans. C) The region around a charge where electrostatic force is experienced.
How is the electric field defined?
A) As the electric force experienced by a unit negative charge.
B) As the electric force experienced by a unit positive charge.
C) As the gravitational force experienced by a unit positive charge.
D) As the magnetic force experienced by a unit positive charge.
Ans. B) As the electric force experienced by a unit positive charge.
How are electric fields represented?
A) By field lines.
B) By electric charges.
C) By vectors.
D) By matrices.
Ans. A) By field lines.
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