Class 10 Physics Unit-13: Electrostatics, Solved MCQs With Verified Answers. (National Book Foundation 2022 as Federal Text Book, Islamabad)

1. How many electrons form a 1C charge?

(a) 1.6 ｘ 10⁻¹⁹
(b) 6.25 ｘ 10⁻¹⁹
(c) 1.6 ｘ 10¹⁹
(d) 6.25 ｘ 10¹⁸

... Answer is (d) 6.25 ｘ 10¹⁸
1.6 ｘ 10⁻¹⁹ C is the charge on one electron, thus 1 C = `\frac {1}{1.6 ｘ 10⁻¹⁹ }` = 6.25 ｘ 10¹⁸ electrons

2. What is the electrostatic force between two charges each of 1 mC separated distance of 1m?

(a) 900 N
(b) 9000 N
(c) 9 ｘ 10⁹ N
(d) 90 N

... Answer is (c) 9 ｘ 10⁹ N
F = K `\frac {q_1q_2}{r^2}`

3. If the distance between charges is doubled, then the force between them becomes:

(a) half
(b) 1/4th
(c) double
(d) 4 times

... Answer is (b) 1/4th
F = K `\frac {q_1q_2}{r^2}`

4. If a charge of 2 C experiences a force of 10 N in the electric field of 5 C charge. Electric field intensity at that point is:

(a) 5 N/ C
(b) 2 N/ C
(c) 10 N/ C
(d) 20 N/ C

... Answer is (a) 5 N/ C
E = F / q (test charge) = 10 N / 2 C = 5 N/C

5. If the potential difference between plates of capacitors is reduced to half, then the capacitance of the capacitor becomes:

(a) half
(b) double
(c) 1/4th
(d) remains same

... Answer is (d) remains the same
Capacitance is independent of the potential difference and the charge.

6. Farad (F) is the unit of:

(a) Potential difference
(b) Electric force
(c) Capacitance
(d) Electric field intensity

... Answer is (c) Capacitance
----------------------

7. If two capacitors are connected in series then the capacitance of their combination: :

(a) Increases
(b) Decreases
(c) Remains same
(d) Always increases 4 times

... Answer is (b) Decreases
`\frac {1}{C_{eq}}` = `\frac {1}{C_1}` + `\frac {1}{C_2}`

8. Which is a vector quantity?

(a) Electric field intensity
(b) Electric potential
(c) Potential difference
(d) Capacitance

... Answer is (a) Electric field intensity
Electric field intensity `\vec E` has both magnitude and direction

9. . If a capacitor stores a charge of 10 C when a potential difference of 5 V is applied, what will be the charge on the capacitor if 20 V is applied to it?

(a) 20 C
(b) 30 C
(c) 40 C
(d) 10 C

... Answer is (c) 40 C
First to find C = Q/V = 10 C/5 V = 2 F. Now to find Q = C V = 2 F x 20 V = 40 C
 

10. Which of the followings is touched with a disc of charged electroscope but the gold leaves of the electroscope do not collapse?

(a) Paper rod
(b) Steel rod
(c) Copper rod
(d) Graphite rod

... Answer is (a) Paper rod
As it is an insulator

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