Physics Multiple Choice Questions on “Basic Properties of Electric Charge”.
1. A solid sphere will carry more charge than a hollow sphere of the same radius.
a) True
b) False
Answer: b
Clarification: Charge is distributed only on the outer surface of a body. As both the spheres have the same radius and same surface area, they will carry the same amount of charge. But the charge carried by a sphere and a cube will be different as their surface areas are different.
2. +q, +2q, +3q, +4q, ……(up to +20q) charges are situated at coordinates (0,0) , (1,0) ,(2,0) , ….. (Up to 20). What is the total charge stored in the system?
a) +20q
b) +210q
c) +420q
d) +190q
Answer: b
Clarification: As charge is additive, total charge will be (1+2+3+4+…. +20)*q=(frac{20*21}{2})*q= 210q. But if the polarities of the charges are different i.e. some of them are positive and some are negative, then the result will be different. We have to add separately the positive charges and the negative charges.
3. A charged conductor has its charge only on its outer surface. This statement is true for which of the following?
a) For all conductors
b) Only for spherical conductors
c) For hollow conductors
d) For those conductors which don’t have sharp edges
Answer: a
Clarification: Charge remains on the outer surface of a conductor, irrespective of the shape and size of the conductor and also for hollow and solid conductors both. But if there is a sharp edge in the conductor, surface charge density will be more at that point. The surface charge density is uniform in the case of a sphere.
4. What is the unit of surface charge density in the SI unit?
a) C
b) C/m
c) C/m2
d) C/m3
Answer: c
Clarification: Surface charge density means how much charge is stored in the unit surface area of a conductor. So, it’s unit will be=(frac{the , unit , of , the , charge}{the , unit , of , area}). In SI the unit of charge is Coulomb and the unit of area is m2. Therefore the required unit will be C/m2.
5. What number of electrons will flow in one minute through a conductor that carries 1 Ampere current?
a) 5.2*1020
b) 4.2*1020
c) 3.7*1020
d) 3.7*1019
Answer: c
Clarification: 1 Ampere means 1 Coulomb per second. So the number of electrons flow per second is ((frac {1}{1.602*10^{-19}})). Therefore number of electron flow in one minute =(frac {1}{1.602*10^{-19}})*60 =3.7*1020.The number will be 60 times more if we have to calculate the number of electron flow in an hour.
6. What is the dimension of volume charge density?
a) [MLAT-2]
b) [M0 L-3 A T]
c) [M L-3 A T]
d) [M L-2 A T]
Answer: b
Clarification: Volume charge density = (frac {charge}{volume}=frac {current*time}{volume}=frac {A*T}{L^3})=[M0 A T L-3]. But in case of surface charge density, the dimension will be [M0 L-2 A T] because surface charge density means an electric charge in a unit area of the surface.
7. Which one of the following is a safe place during lightning?
a) Under a tree
b) Under a light post
c) House with lightning arrester
d) High wall
Answer:c
Clarification: Lightning arrester arrests lightning and allows a safe path of electricity to ground. Thus it is a safe place inside a house that has a lightning arrester on the top of it. Else, electricity finds a high tower or tree or wall and travels through them to ground. Therefore these are not safe places to take shelter during lightning.
8. What should be the shape of a conductor that can hold a charge for long?
a) Cubical
b) Conical
c) Sharp-edged
d) Spherical
Answer: d
Clarification: Sphere has uniform charge distribution over its entire surface. It doesn’t have any sharp edges hence very little chance of charge accumulation at those edges and hence very little chance of discharge of stored charge.
9. A lightning arrester must have the following property.
a) Discontinuity
b) Poor conductivity
c) Needle end
d) Low melting point
Answer: c
Clarification: Needle end can arrest the lightning easily. Besides, the device must provide a continuous path to electricity so that current passes to ground. It must have a high melting point else it will meltdown due to the heat generated during carrying lightning current.
10. Earth is the source of __________
a) An infinite positive and negative charge
b) Positive charge
c) Negative charge
d) Zero charge
Answer: a
Clarification: Earth can be considered as an infinite source of positive and negative charges. This can be justified by the fact that if we connect any positive or negatively charged body to the ground, all of its charges will go to earth.
11. Which one is not the property of charge?
a) Charge is additive
b) Charge is conserved
c) Quantization of charge
d) A charge is self-destructive
Answer: d
Clarification: Electric charge possesses the properties of quantization, conservation of charge. It cannot be destroyed i.e. it is not self-destructive.