CBSE Questions for Class 12 Medical Physics Electric Charges And Fields Quiz 1 - MCQExams.com

Five ball numbered $$1$$ to $$5$$ are suspended using separate threads. Pairs $$(1,2)$$, $$(2,4)$$ and $$(4,1)$$ show electrostatic attraction while pairs $$(2,3)$$, $$(4,5)$$ show repulsion. Therefore, ball $$1$$ must be
  • neutral
  • metallic
  • positively charged
  • negatively charged
The magnitude of charges of electric dipole is $$3.2 \times {10^{ - 5}}$$ and distance between them is $$2.4A.$$ If it is placed in an electric field $$4 \times {10^5}\,V/m$$ then its diple moment is (in C-m)
  • $$9.6 \times {10^{ - 5}}$$
  • $$12.8 \times {10^{ - 14}}$$
  • $$7.68 \times {10^{ - 15}}$$
  • $$30.72 \times {10^{ - 24}}$$
The electric field in a region is given by $$\vec { E } =a\hat { i } +b\hat { j } $$. Here a and b are constants. Find the net flux passing through a square area of side $${ L }_{ 0 }$$  parallel to y-z plane
  • $$a{ L }_{ 0 }^{ 3 }$$
  • $$2a{ L }_{ 0 }^{ 2 }$$
  • $$a{ L }_{ 0 }^{ 2 }$$
  • $$\left( a+b \right) { L }_{ 0 }^{ 2 }$$
The nature of charge on the object can be detected by:
  • Microscope
  • Electroscope
  • Electrometer
  • Telescope
A cone of base radius $$R$$ and height $$h$$ is located in a uniform electric field $$\overrightarrow{E}$$ parallel to its base. The electric flux entering the cone is:
  • $$4 E h R$$
  • $$\displaystyle \dfrac{1}{2}$$ $$E h R$$
  • $$2 E h R$$
  • $$E h R$$
The electric field in a region of space is given by $$\vec E=E_0\hat i+2 E_o\hat j$$ where $$E_o=100 N/C$$. The flux of this field through a circular surface of radius $$0.02$$ m parallel to the Y-Z plane is nearly :
  • $$0.125 Nm^2/C$$
  • $$0.02 Nm^2/C$$
  • $$0.005 Nm^2/C$$
  • $$3.14 Nm^2/C$$
The magnitude of the average electric field normally present in the atmosphere just above the surface of the Earth is about $$150 N/C$$, directed inward towards the center of the Earth. This gives the total net surface charge carried by the Earth to be : [Given $$\epsilon_0=8.85\times 10^{-12} C^2/N-m^2, R_E=6.4\times 10^6m]$$
  • $$+660 kC$$
  • $$-660 kC$$
  • $$-680 kC$$
  • $$+680 kC$$
......... Charge is produced by friction
  • Stationary
  • No
  • Attractive
  • All
A few electric field lines for a system of two charges $$Q_{1}$$ and $$Q_{2}$$ fixed at two different points on the $$x$$-axis are shown in the figure. These lines suggest that

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  • $$ |Q_{1}|>|Q_{2}|$$
  • $$ |Q_{1}|<|Q_{2}|$$
  • at a finite distance to the left of $$Q_{1},$$ the electric field is zero
  • at a finite distance to the right of $$Q_{2},$$ the electric field is zero
Consider an electric field $$\overline{E}=E_{0}\hat{x}$$, where $$E_{0}$$ is a constant. The flux through the shaded area (as shown in the figure) due to this field is:

28712.PNG
  • $$2E_{0}a^{2}$$
  • $$\sqrt{2}E_{0}a^{2}$$
  • $$E_{0}a^{2}$$
  • $$\displaystyle \dfrac{E_{0}a^{2}}{\sqrt{2}}$$

A point charge $$+Q$$ is placed just outside an imaginary hemispherical surface of radius $$R$$ as shown in the figure. Which of the following statements is/are correct? 

640588_ca215d0993e4422e952afc9656cbb73c.png
  • The electric flux passing through the curved surface of the hemisphere is $$-\dfrac{Q}{2\in _0} \left(1-\dfrac{1}{\sqrt{2}}\right)$$
  • The component of the electric field normal to the flat surface is constant over the surface
  • Total flux through the curved and the flat surface is $$\dfrac{Q}{\in_0}$$
  • The circumference of the flat surface is an equipotential
A cubical region of side a has its centre at the origin. It encloses three fixed point charges, -q
at (0, -a/4, 0), +3q at (0, 0, 0) and -q at (0, +a/4 ,0). Choose the correct option(s):

28855.png
  • The net electric flux crossing the plane x = +a/2 is equal to the net electric flux crossing the plane x = -a/2
  • The net electric crossing the plane y = +a/2 is more than the net electric flux crossing the plane y = -a/2
  • The net electric flux crossing the entire region is $$\frac { q }{ { \varepsilon }_{ o } } $$
  • The net electric flux crossing the piane z = +a/ 2 is equal to the riet electric flux crossing the piane x = +a/2
In a certain region of space, electric field is along the z-direction throughout. The magnitude of electric field is however not constant, but increases uniformly along the positive z-direction at the rate of $$10^{5}N\ C^{-1}m^{-1}$$. The force experienced by the system having a total dipole moment equal to $$10^{-7}C\ m$$ in the negative $$z-direction$$ is
  • $$-10^{-2}N$$
  • $$10^{-2}N$$
  • $$10^{-4}N$$
  • $$-10^{-4}N$$
  • Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.
  • Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.
  • Assertion is correct but Reason is incorrect.
  • Both Assertion and Reason are incorrect.
Electric field outside a long wire carrying charge q is proportional to :
  • $$\dfrac { 1 }{ r } $$
  • $$\dfrac { 1 }{ { r }^{ 2 } } $$
  • $$\dfrac { 1 }{ { r }^{ \frac { 1 }{ 3/5 } } } $$
  • $$\dfrac { 1 }{ { r }^{ \frac { 1 }{ 3/2 } } } $$
An electric line of force in the $$xy-plane$$ is given by equation $$x^{2} + y^{2} = 1$$. A particle with unit positive charge, initially at rest at the point $$x = 1, y = 0$$ in the $$xy - plane$$.
  • Not move at all
  • Will move along straight line
  • Will move along the circular line of force
  • Information is insufficient to draw any conclusion
Complete the following statements with an appropriate word /term be filled in the blank space(s).

The force of attraction or repulsion between two charges is given by ......................
  • Gauss's law
  • Kepler's law
  • Coulomb's law
  • Gravitational law

If the flux of the electric field through a closed surface is zero:
  • the electric field must be zero everywhere on the surface
  • the electric field must not be zero everywhere on the surface
  • the charge inside the surface must be zero
  • the charge in the vicinity of the surface must be zero

Electric field intensity at a point due to an infinite sheet of charge having surface charge density $$\sigma $$ is $$E$$. If  the sheet were conducting, electric intensity would be
  • $$\dfrac{E}{2}$$
  • $$E$$
  • $$2 E$$
  • $$4 E$$

Number of electric lines of force emanating from $$1C$$ of positive charge in vacuum is :
  • $$8.85\times10 ^{-12}$$
  • $$9\times10 ^{9}$$
  • $$1/4\pi \times 9\times 10^{9}$$
  • $$1.13\times10 ^{11}$$
Lightning is a ________ phenomenon
  • Electromagnetic
  • Current electricity
  • Electrochemical
  • Electrostatic
An infinite plane sheet of a metal is charged to charge density $$\sigma\ C/m^{2}$$ in a medium of dielectric constant K. Intensity of electric field near the metallic surface will be :
  • $$E=\dfrac{\sigma }{\varepsilon _{_{0}}K}$$
  • $$E=\dfrac{\sigma }{2\varepsilon _{_{0}}}$$
  • $$E=\dfrac{\sigma }{2\varepsilon _{_{0}}K}$$
  • $$E=\dfrac{K\sigma }{2\varepsilon _{_{0}}}$$
When we remove polyester or woollen clothes in dark, we can see a spark and hear a crackling sound. Which of the following is responsible for it?
  • Static electricity.
  • Current electricity.
  • Reflection of light.
  • Refraction of light.
Two charged objects are brought close to each other. Choose the most appropriate statement from the following options:
  • they may attract
  • they may repel
  • they may attract or repel depending on the type of charges they carry
  • there will be no effect

Two thin infinite parallel sheets have uniform surface densities of charge $$+\sigma$$ and $$-\sigma .$$ The value of $$E$$ in the space outside the sheets is:
  • $$\dfrac {\sigma}{\epsilon _{0}}$$
  • $$\dfrac{\sigma}{2\epsilon _{0}}$$
  • zero
  • $$\dfrac{2\sigma}{\epsilon _{0}}$$
$$Debye$$ is the unit of:
  • electric flux
  • electric dipole moment
  • electric potential
  • electric field intensity
What is the nature of electric charge?
  • only positive
  • only negative
  • positive and negative both
  • neutral.
State whether the following statements are True or False.
If E=0, at all points of a closed surface, The electric flux through the surface is zero.
  • True
  • False
True Or False?
1)A proton repels an electron.
2)An electron repels a proton.
  • False, False
  • True, True
  • True, False
  • False, True.
The ampere-sec stands for the unit of :
  • Power
  • Current
  • Energy
  • Charge
Electroscope is an instrument used to find the quantity of charge on different bodies.
  • True
  • False
Debye is the unit of
  • Electric flux
  • Electric dipole moment
  • Electric potential
  • Electric field intensity
Which of the following charge is acquired by silk when the silk is rubbed with glass?
  • Positive
  • Negative
  • Nuetral
  • Can not be determined
The laws of forces that govern the force between two electric charges were discovered by :
  • Faraday
  • Ampere
  • Ohm
  • Coulumb
The solid angle subtended by the total surface area of a sphere at the centre is :
  • $$4\pi$$
  • $$2\pi$$
  • $$\pi$$
  • $$3\pi$$
An electric dipole is a pair of _______ and ______ charges.
  • equal, same
  • equal, opposite
  • different, same
  • different, opposite
What is the net charge on an neutral atom?
  • positive
  • negative
  • zero
  • none of these
What do you understand by the static or frictional electricity ?
  • Discarging of two bodies on rubbing them together is called static or frictional electricity.
  • Charging of two bodies on rubbing them together is called static or frictional electricity.
  • Electricity which is static is called static or frictional electricity.
  • Electricity on high friction bodies is called static or frictional electricity.
What happens when some charge is placed on a soap bubble?
  • Its radius decreases
  • Its radius increases
  • The bubble collapses
  • None of these
State whether true or false:
Like charges attract each other.
  • True
  • False
Which are the kinds of charges?
  • Positive
  • Negative
  • Both A & B
  • None
When a silk handkerchief is rubbed with glass the charge acquired by silk is :
  • positive
  • negative
  • neutral
  • none of these
Electric field lines of force
  • exist everywhere
  • exist only in the immediate vicinity of electric charges
  • exist only when both positive and negative charges are near one another
  • are imaginary
In a region of space having a uniform electric field $$E$$, a hemispherical bowl of radius $$r$$ is placed. The electric flux $$\phi$$ through the bowl is
  • $$2\pi RE$$
  • $$4\pi {R}^{2}E$$
  • $$2\pi {R}^{2}E$$
  • $$\pi {R}^{2}E$$
State whether true or false:
Unlike charges attract each other.
  • True
  • False
A negatively charged ebonite rod is brought near the glass rod which has been robbed on silk. State your observation between them
  • Attraction
  • Repulsion
  • No change
  • cant say
Two uncharged bodies on rubbing, get charged due to:
  • conduction
  • friction
  • induction
  • none of these
When we remove polyester or woollen cloth in dark, we can see sparkand hear a cracking sound. These are due to:
  • static electricity
  • current electricity
  • reflection of light
  • refraction of light
State the kind of charge on a positive ion :
  • Positive
  • Negative
  • zero
  • cant say
Complete the following sentences:
A glass rod is rubbed with silk. The charge on glass rod is ...... and the charge on silk is ......
  • $$positive, positive$$
  • $$negative, negative$$
  • $$positive, negative$$
  • $$negative, positive$$
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