# Class 12 Physics Chapter 1 Case Study Question Electric Charges and Fields PDF Download

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 Electric Charges and Fields to know their preparation level.

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

Question 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 10-19 C the charge of the electron. For this, he won the Nobel prize.

(i) If a drop of mass 1.08 x 10-14 kg remains stationary in an electric field of 1.68 x 105 N C-I, then the charge of this drop is

Answer: (a) 6.40 x 10-19 C

(ii) Extra electrons on this particular oil drop (given the presently known charge of the electron) are

(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)

(iv) The important conclusion given by Millikan’s experiment about the charge is

(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

Question 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 electro statics 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

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