CBSE Questions for Class 12 Medical Physics Electrostatic Potential And Capacitance Quiz 5 - MCQExams.com

A photographic flash unit consists of a xenon-filled tube. It gives a flash of average power $$2000W$$ for $$0.04s$$. The flash due to discharge of a fully charged capacitor of $$40\mu F$$. The voltage to which it is charged before a flash is given by the unit is :
  • $$1500V$$
  • $$2000V$$
  • $$2500V$$
  • $$3000V$$
An electron is taken from point $$A$$ to point $$B$$ along the path $$AB$$ in a uniform electric field of intensity $$\displaystyle E = 10 Vm^{-1}$$. Side $$AB = 5 m$$, and side $$BC = 3 m$$. Then, the amount of work done on the electron by us is :
155254_425ab2a56a484bdea08b2b6d58703432.png
  • 50 eV
  • 40 eV
  • -50 eV
  • -40 eV
A thin metallic spherical shell contains a charge $$Q$$ on its surface. A point charge $$q_{1}$$ is placed at the centre of the shell and another charge $$q_{2}$$ is placed outside the shell. All the three charges are positive. Then, the force on charge $$q_{1}$$ is
195226_5637bd1ea75b4fb89ec2f81025e1f2c4.PNG
  • Towards left
  • Towards right
  • Upward
  • Zero
Which of the following factors do not influence the capacity of a capacitor?
  • distance between the plates
  • material of the plates
  • area of the plates
  • curvature of the plates
Two identical parallel plate capacitors are connected in series and then joined in series with a battery of $$100V$$. A slab of dielectric constant $$K=3$$ is inserted between the plates of the first capacitor. Then, the potential difference across the capacitors will be respectively,
  • $$25V, 75V$$
  • $$75V, 25V$$
  • $$20V, 780
  • $$50V, 50V$$
The separation between the plates of $$C_1$$ of Fig is doubled and a dielectric of strength 6 is added in between the plates of $$C_2$$. Find the the change in potential drop across $$C_1$$ and $$C_2$$:
150592_679cefd6e3e54db29980155454efe5bd.png
  • $$\Delta V_1=\dfrac{11C_2V_0C_1}{(C_1+12C_2)(C_1+C_2)}(increases)$$

    $$\Delta V_2=\dfrac{11C_1C_2V_0}{(C_1+C_2)(C_1+12C_2)}(decreases)$$
  • $$\Delta V_1=\dfrac{11C_2V_0C_1}{(C_1+12C_2)(C_1+C_2)}(decreases)$$

    $$\Delta V_2=\dfrac{11C_1C_2V_0}{(C_1+C_2)(C_1+12C_2)}(increases)$$
  • $$\Delta V_1=\dfrac{22C_2V_0C_1}{(C_1+12C_2)(C_1+C_2)}(increases)$$

    $$\Delta V_2=\dfrac{22C_1C_2V_0}{(C_1+C_2)(C_1+12C_2)}(decreases)$$
  • $$\Delta V_1=\dfrac{22C_2V_0C_1}{(C_1+12C_2)(C_1+C_2)}(decreases)$$

    $$\Delta V_2=\dfrac{22C_1C_2V_0}{(C_1+C_2)(C_1+12C_2)}(increases)$$
A hollow insulated conducting sphere is given a positive charge of $$10\mu C$$. What will be the electric field at the centre of the sphere if its radius is $$2$$ metres?
  • zero
  • $$5\mu C{m}^{-2}$$
  • $$20\mu C{m}^{-2}$$
  • $$8\mu C{m}^{-2}$$
A parallel plate capacitor is charged to a certain voltage. Now, if the dielectric material (with dielectric constant k) is removed then the
  • capacitance increases by a factor of k
  • electric field reduces by a factor k
  • voltage across the capacitor decreases by a factor k
  • none of these
A foil of aluminium of negligible thickness is inserted in between the space of a parallel plate condenser. If the foil is electrically insulated, the capacity of the condenser will :

199389_366a9f1bd86941e6bb8080c5eb887596.png
  • increase
  • decrease
  • remain unchanged
  • become zero
For a given potential difference V how would you connect two capacitors, to obtain greater stored charge :
  • series
  • parallel
  • series and parallel combined
  • cannot say
If in a parallel plate capacitor, which is connected to a battery, we fill dielectrics in whole space of its plates, then which of the following increases?
  • Q and V
  • V and E
  • E and C
  • Q and C
In a charged capacitor, the energy is stored in :
  • the negative charges
  • the positive charges
  • the field between the plates
  • both 'a' and 'b'
A positive point charge q is carried from a point B to a point A in the electric field of a point charge $$+$$Q held at O. If the permittivity of free space is $$\epsilon_0$$ and OA=a and OB=b, the work done in the process is given by :

  • $$\dfrac {qQ}{4\pi \epsilon_0}\left (\dfrac {1}{a}+\dfrac {1}{b}\right )$$

  • $$\dfrac {qQ}{4\pi \epsilon_0}\left (\dfrac {1}{a}-\dfrac {1}{b}\right )$$

  • $$\dfrac {qQ}{4\pi \epsilon_0}\left (\dfrac {1}{a^2}-\dfrac {1}{b^2}\right )$$

  • $$\dfrac {qQ}{4\pi \epsilon_0}\left (\dfrac {1}{a^2}+\dfrac {1}{b^2}\right )$$

Two parallel metal plates having charges +Q and -Q face each other at a certain distance between them. If the plates are now dipped in kerosene oil tank, the electric field between the plates will :
  • remain same
  • become zero
  • increase
  • decrease
If the potential of a capacitor having capacity of $$6\mu F$$ is increased from 10 V to 20 V, then increase in its energy will be :
  • $$4\times 10^{-4}J$$
  • $$5\times 10^{-4}J$$
  • $$9\times 10^{-4}J$$
  • $$12\times 10^{-6}J$$
A sheet of aluminium foil of negligible thickness is introduced between the plates of a capacitor. The capacitance of the capacitor :
  • decreases
  • remains unchanged
  • becomes infinite
  • increases
A parallel plate condenser is immersed in an oil of dielectric constantThe field between the plates is :
  • increased, proportional to $$\frac {1}{2}$$
  • decreased, proportional to -2
  • increased, proportional to -2
  • decreased, proportional to $$-\frac {1}{2}$$
Two capacitors of capacitance $$C_1$$ and $$C_2$$ are connected in parallel across a battery. If $$Q_1$$ and $$Q_2$$ respectively be the charges on the capacitors, then $$\dfrac {Q_1}{Q_2}$$ will be equal to :
  • $$\dfrac {C_2}{C_1}$$
  • $$\dfrac {C_1}{C_2}$$
  • $$\dfrac {C_1^2}{C_2^2}$$
  • $$\dfrac {C_2^2}{C_1^2}$$
The work done in placing a charge of $$8\times 10^{-18}$$ coulomb on a condenser of capacity 100 micro-farad is :
  • $$3.1\times 10^{-26}J$$
  • $$4\times 10^{-10} J$$
  • $$32\times 10^{-32} J$$
  • $$16\times 10^{-232} J$$
A parallel plate condenser with oil between the plates (dielectric constant of oil $$K=2)$$ has a capacitance C. If the oil is removed, then capacitance of the capacitor becomes :
  • $$\sqrt 2C$$
  • $$2C$$
  • $$\dfrac {C}{\sqrt 2}$$
  • $$\dfrac {C}{2}$$
Two metal spheres of radii a and b are connected by a thin wire. Their separation is very large compared to their dimensions. The capacitance of this system is :
  • $$4\pi \varepsilon_o(ab)$$
  • $$2\pi \varepsilon_o(a+b)$$
  • $$4\pi \varepsilon_o(a+b)$$
  • $$4\pi \varepsilon_o\left (\dfrac {a^2+b^2}{2}\right )$$
Two capacitors of capacitance C are connected in series. If one of them is filled with dielectric substance k, what is the effective capacitance?
  • $$\frac {kC}{(1+k)}$$
  • C(k+1)
  • $$\frac {2kC}{1+k}$$
  • none of these
Find the dimensions of capacitance :
  • $$=[M^{-1}L^{2}T^4A^{-2}]$$
  • $$=[M^{-1}L^{-2}T^{-4}A^2]$$
  • $$=[M^{-1}L^{-1}T^4A^2]$$
  • $$=[M^{-1}L^{-2}T^4A^2]$$
No charge will flow when two conductors having the same charge are connected to each other. 
Given statement is:
  • True
  • False
The electric potential inside a conductor:
  • is zero
  • increases with distance from center
  • is constant
  • decreases with distance from center
If a capacitor $$900\mu F$$ is charged to $$100 V$$ and its total energy is transferred to a capacitor of capacitance $$100 \mu F$$ then its potential is :
  • $$200 V$$
  • $$30 V$$
  • $$300 V$$
  • $$400 V$$
If a slab of insulating material $$4\times 10^{-5}m$$ thick is introduced between the plates of a parallel plate capacitor, the distance between the plates has to be increased by $$3.5\times 10^{-5}m$$ to restore the capacity to original value. Then the dielectric constant of the material of slab is :
  • $$8$$
  • $$6$$
  • $$12$$
  • $$10$$
If we increase '$$d$$' of a parallel condenser to '$$2d$$' and fill wax to the whole empty space between its two plate, then capacitance increase from $$1pF$$ to $$2pF$$. What is the dielectric constant of wax?
  • $$2$$
  • $$4$$
  • $$6$$
  • $$8$$
An air capacitor C connected to a battery of e.m.f. V acquires a charge q and energy E. The capacitor is disconnected from the battery and a dielectric slab is placed between the plates. Which of the following statements is correct?
  • V and q decrease but C and E increase
  • V remains unchange, but q, E and C increase
  • q remains unchanged, C increases, V and E decrease
  • q and C increase but V and E decrease
A bullet of mass $$2 g$$. is having a charge of $$2\:\mu C$$. Through what potential difference must it be accelerated, starting from rest, to acquire a speed of $$10\:m/s$$?
  • $$5 MV$$
  • $$5V$$
  • $$50 V$$
  • $$5 kV$$
In moving from $$A$$ to $$B$$ along an electric field line, the electric field does $$1.28\times {10}^{-18}J$$ of work on an electron. If $${\phi}_{1}, {\phi}_{2}$$ are equipotential surface, then potential difference $${V}_{E}-{V}_{D}$$ is equal to :
292025.PNG
  • $$-8$$ volt
  • $$+8$$ volt
  • zero
  • $$64$$ volt
A capacitor becomes a perfect insulator for
  • alternating current
  • direct current
  • both (a) and (b)
  • None of these
The associated figure shows an electric charge $$+q$$ located at the centre of a hollow uncharged conducting metal sphere. Outside the sphere is a second charge $$+Q$$. Both charges are positive. Choose the description below that describes the net electrical forces on each charge in this situation.
303601_c1eb1d427eec438d99fcfa0582e4abd7.png
  • $$Both\ charges \ experience \ the \ same \ net \ force \ directed \ away \ from \ each \ other.$$
  • $$No \ net \ force \ experienced \ by \ either \ charge.$$
  • $$There \ is \ no \ net \ force \ on \ Q \ but \ a \ net \ force \ on \ q.$$
  • $$There \ is \ no \ net \ force \ on \ q \ but \ a \ net \ force \ on \ Q.$$
  • $$Both \ charges \ experience \ a \ net \ force \ but \ they \ are \ different \ from \ each \ other.$$
A point charge $$q_1 = q$$ is placed at point P. Another point charge $$q_2 = - q$$ is placed at point Q. At some point $$R(R \neq p, R \neq Q)$$ electric potential due to $$q_1$$ is $$V_1$$ and electric potential due to $$q_2$$ is $$V_2$$. Which of the following is correct?
  • Only for some points $$V_1 > V_2$$,
  • Only for some points $$V_2 > V_1$$,
  • For all points $$V_1 > V_2$$
  • For all points $$V_2 > V_1$$
An electrical charge $$2 \times 10^{-8}$$ C is placed at the point (1, 2, 4 )m. At the point (4, 2, 0) m, the electric
  • potential will be 36 V
  • field will be along y-axis
  • field will increase if the space between the points is filled with a dielectric
  • All of the above
A charge of 5 C is moved between two points in an electric field and 20 J of work was done to do so. Calculate the potential difference between the two points
  • 4 V
  • 2 V
  • 3 V
  • 6 V
Let S be the set of all points in a plane. Let R be a relation on S such that for any two points a and b, aRb iff b is within 1 cm from a. Then R is
  • Equivalence relation
  • Reflexive and symmetric not transitive
  • Reflexive and transitive not symmetric
  • Symmetric and transitive not reflexive
Which of the following is not a unit for electric potential?
  • Volt
  • Joule/coulomb
  • Erg/stat coulomb
  • None of these
$$ECG$$ is a method of diagnosis used to check the functioning of heart, it is based on the principle that there is
  • A pattern of magnetic field associated with the functioning of heart
  • An electrical impulse associated with the functioning of organs and tissues of human body
  • A varying electrical field associated. with organs and tissues of human body
  • A varying magnetic field associated with organs and tissues of human body
The electric potential at the surface of an atomic nucleus (Z = 50) of radius $$9.0 \times 10^{-13} cm$$ is:
  • $$ 9\times 10^5$$ volt
  • $$ 8 \times 10^6$$ volt
  • 80 volt
  • 9 volt
what is the potential difference between two points, if 2J of work must be done to move a 4 mC charge from one point to another is:
  • 50 V
  • 500 V
  • 5 V
  • 5000 V
Identify the correct statement from below:

451349_ed0eacd4d39a4cb1a584f2eea05722d8.png
  • A will be at higher potential
  • B will be at higher potential
  • Both will be at same potential
  • Can't be said
Assertion: A parallel plate capacitor is connected across battery through a key. A dielectric slab of dielectric constant K is introduced between the plates. The energy which is stored becomes K times.
Reason: The surface density of charge on the plate remains constant or unchanged. 
  • If both assertion and reason are true but the reason is the correct explanation of assertion.
  • If both assertion and reason are true but the reason is not the correct explanation of assertion.
  • If assertion is true but reason is false.
  • If both the assertion and reason are false.
  • If reason is true but assertion is false.
Assertion: If the distance between parallel plates of a capacitor is halved and dielectric constant is three times, then the capacitance becomes 6 times.
Reason : Capacity of the capacitor does not depend upon the nature of the material.
  • If both assertion and reason are true but the reason is the correct explanation of assertion.
  • If both assertion and reason are true but the reason is not the correct explanation of assertion.
  • If assertion is true but reason is false.
  • If both the assertion and reason are false.
  • If reason is true but assertion is false.
Among identical spheres A and B having charges $$-15\ C$$ and $$-16\ C$$:
  • $$-15\ C$$ is at higher potential
  • $$-16\ C$$ is at higher potential
  • both are at equal potential
  • no such comparison can be made
A parallel plate air capacitor has a capacitance $$C$$.When it is half filled with a dielectric of dielectric constant $$5$$, the percentage increase in the capacitance will be :
  • $$400$$ %
  • $$66.6$$ %
  • $$33.3$$$ %
  • $$200$$ %
A capacitor is charged by using a battery which is then disconnected. A dielectric slab is introduced between the plates which results in :
  • increase in the potential difference across  the plates and reduction in stored energy but no change in the charge on the plates
  • decrease in the potential difference across the plates and reduction in the stored energy but no change in the charge on the plates
  • reduction of charge on the plates and Increase of potential difference across the plates
  • increase in stored energy but no change in potential difference across the plates
Three condenser of capacitance $$C(\mu F)$$ are connected in parallel to which a condenser of capacitance $$C$$ is connected in series. Effective capacitance is $$3.75$$, then capacity of each condenser is
  • $$4\mu F$$
  • $$5\mu F$$
  • $$6\mu F$$
  • $$8\mu F$$
"The work per unit of charge required to move a charge from a reference point to a specified point, measured in joules per coulomb or volts. The static electric field is the negative of the gradient of the electric potential." comments are given below ,select the correct one
  • Statement is correct
  • Statement is incorrect
  • Comment on electric field is not correct
  • Only comment on electric potential is not correct
Three particles, each having a charge of $$10\;\mu C$$ are placed at the corners of an equilateral triangle of side $$10\ cm$$. The electronic potential energy of the system is: (Given $$\dfrac{1}{4\pi \varepsilon_0}=9\times10^9N-m^2/C^2$$)
  • $$Zero$$
  • Infinite
  • $$27\;J$$
  • $$100\;J$$
0:0:1


Answered Not Answered Not Visited Correct : 0 Incorrect : 0

Practice Class 12 Medical Physics Quiz Questions and Answers