Electric Charges Questions and Answers [Electric Charges and Fields]

These Electric Charges Questions and Answers are most important for your upcoming Physics examinations where a major portion of questions are asked from the chapter Electric Charges and Fields. These Electric Charges Questions and Answers are prepared by our team to help you.

Electric Charges Questions and Answers

1. If an object is positively charged, theoretically the mass of the object ______

a) Increases slightly by a factor of 9.11*10-31 kg

b) Decreases slightly by a factor of 9.11*10-31 kg

c) Remains the same

d) May increase or decrease

Answer: b
Explanation: If an object is positively charged it loses some of its electrons. The mass of an electron is 9.11*10-31 kg. So, if a positively charged body loses ‘n’ number of electrons, it mass decrease by the amount n*9.11E-31kg.

2. Why is gold used in the Gold-leaf electroscope?

a) Gold is easily available in nature

b) Gold is malleable

c) Gold is conducting in nature

d) Gold is cheap

Answer: b
Explanation: Though gold is a costly metal it is used in electroscope because of the property malleability. This means very thin and light sheets can be formed from gold simply by hammering or rolling and hence the deflection of the light gold plates increases.

3. What happens to the plates of the apparatus if we measure alternating charge using a Gold-leaf oscilloscope?

a) It doesn’t diverge at all

b) It diverges momentarily

c) The plates give a proper divergence

d) The degree of divergence increases and decreases repeatedly

Answer: c
Explanation: The divergence of the plates of the Gold-leaf oscilloscope depends only on the presence of a charge, not on the quality of charge i.e. positive or negative. So, if the charge changes from positive to negative and vice versa the degree of divergence of the plates remains the same.

4. Dr. Gilbert tried to hold a brass rod by hand and induce static electricity in it by friction. Why did he fail?

a) Static electricity is induced only on insulators while brass is conducting

b) The induced static charge flew through his hand and body to the ground

c) The static charge was not produced at all

d) It is not possible to induce static electricity by friction

Answer: b
Explanation: The human body is a good conductor and hence the charge produced by friction flew through his body to the ground. We can tackle the problem simply by holding the brass rod with the help of some insulated holder.

5. Gold-leaf electroscope can be used _______

a) Only to detect the presence of charge

b) To detect the presence of charge as well as its nature (positive or negative)

c) To measure the surface charge density

d) To measure current

Answer: b
Explanation: If the apparatus is initially in contact with some positively charged body and then comes in contact with another charged body and if the divergence increases we can deduce that the second body is also positively charged. If the divergence decreases then the second body must be negatively charged.

6. 1 Coulomb = ________ Electro Static Unit.

a) 3*109

b) 3*108

c) 1.602*10-19

d) 2*109

Answer: a
Explanation: 1 Coulomb means 3*109 Electro Static Unit of charge. Coulomb and ESU are two different units of charge and their conversion formula is necessary. Coulomb is the unit of charge in the SI system and esu is the unit of charge in the CGS system.

7. Number of electrons in 1 Coulomb charge is _________

a) 6.25*1021

b) 6.25*1020

c) 6.25*1025

d) 6.25*1023

Answer: a
Explanation: Electron has the charge of 1.602*10-19 Coulomb. So, the number of electrons in 1 Coulomb of charge is \(\frac{1}{1.602*10^{-19}}\) = 6.25*1021. This huge number of electrons can be accumulated to form 1C of charge. Thus, we can conclude that we need Avogadro’s number of electrons (approximately) to get 100C charges.

8. Two equally charged spheres attract each other. Now if they touch each other then they will _____

a) Attract each other with the same amount of force

b) Repel each other

c) Attract each other with less amount of force

d) Don’t attract or repel

Answer: d
Explanation: The two spheres are oppositely charged by the same amount. So if they come in contact, both of their charges are neutralized. So they become uncharged and don’t attract or repel each other.

9. Which among the following cannot be the charge of a charged body?

a) 4.8*10-14 Coulomb

b) 6.4*10-15 Coulomb

c) 5*10-14 Coulomb

d) 3.2*10-10 Coulomb

Answer: c
Explanation: Charge of a body must be an integral multiple of charge of an electron. 5*10-14 is not an integral multiple of (1.602*10-19 Coulomb) which is equal to the charge of an electron. But we can see that 4.8, 6.4, 3.2 are integral multiples of 1.6.