Physics Test 4 - Electrostatics, Capacitance, Current Electricity


30 Questions MCQ Test JEE Main Mock Test Series 2020 & Previous Year Papers | Physics Test 4 - Electrostatics, Capacitance, Current Electricity


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This mock test of Physics Test 4 - Electrostatics, Capacitance, Current Electricity for JEE helps you for every JEE entrance exam. This contains 30 Multiple Choice Questions for JEE Physics Test 4 - Electrostatics, Capacitance, Current Electricity (mcq) to study with solutions a complete question bank. The solved questions answers in this Physics Test 4 - Electrostatics, Capacitance, Current Electricity quiz give you a good mix of easy questions and tough questions. JEE students definitely take this Physics Test 4 - Electrostatics, Capacitance, Current Electricity exercise for a better result in the exam. You can find other Physics Test 4 - Electrostatics, Capacitance, Current Electricity extra questions, long questions & short questions for JEE on EduRev as well by searching above.
QUESTION: 1

Figure shows some of the electric field lines corresponding to an electric field. The figure suggests that 

Solution:

At point A and C, electric field lines are dense and equally spaced, so EA = EC
While at B they are far apart.
∴ EA = E> EB

QUESTION: 2

When the separation between two charges is increased, the electric potential energy of the charges 

Solution:

Potential  energy between two charges 
Now if r increases and q1 and q2 are of same sign then
 decrases. if q1 and q2 are of opposite  increases.
Therefore depending on signs of q1 and q may increase or decrease.

QUESTION: 3

An electric dipole is placed in a uniform electric field. The net electric force on the dipole 

Solution: As dipole is combination of equal positive and negative charges, when an electric field is generated in the region of the dipole, torque can act on the dipole, but there will be no force on the dipole.
QUESTION: 4
Electric charge are distributed in a small volume. The flux of the electric field through a spherical surface of radius 10cm surrounding the total charge is 25V-m The flux over a concentric sphere of radius 20cm will be
Solution:
QUESTION: 5

A charge q is placed at the centre of the open end of a cylindrical vessel in figure. The flux of the electric field through the surface of the vessel is 

Solution:

when a charge Q is placed at the centre of the open end of a cylindrical vessel then only half of the charge will contribute to the flux,because half will lie inside the surface and half will outside the surface so flux=Q/2ε0

QUESTION: 6
Mark the correct option 
Solution:
QUESTION: 7

Two capacitors each having capacitance C and breakdown voltage V are joined in series. The capacitance and the breakdown voltage of the combination will be 

Solution:

QUESTION: 8

A dielectric slab is inserted between the plates of an isolated capacitor. The force between the plates will 

Solution:
Here,the capacitor is isolated. It is already charged or else there would be no force. But when the dielectric is inserted, the charge remains fixed. If the capacitor were connected to a voltage source, then current would flow to keep the voltage fixed and then the force would increase.The voltage goes down even though there is no current in or out.The permittivity of any material is greater than the permittivity of free space. Therefore,When we insert the dielectric slab the capacitance rises.

 
QUESTION: 9

Two metal spheres of capacitances C1 & C2   carry some charges. They are put in contact and then separated. The final charges Q1  and Q2  on them will satisfy

Solution:
QUESTION: 10

Two resistances R and 2R are connected in parallel in an electric circuit. The thermal energy developed in R and 2 R are in the ratio 

Solution:

Thermal energy = V2t/R
In parellel arrangement V is constant
So, for a time t
Thermal energy ∝ 1/R
Ratio of their thermal energy = R₂ : R₁ = 2R : R = 2 : 1

QUESTION: 11
A uniform wire of resistance 50  is cut into 5 equal parts. These parts are now connected in parallel. The equivalent resistance of the combination is
Solution: Each part resistance is 10 ohm as R is directly proportional to length now 10 ohms 5 resistance are connected in parallel. Therefore 2 is equivalent resistance.
QUESTION: 12
The net resistance of an ammeter should be small to ensure that 
Solution: Based on basic construction and implementation of ammeter,it is in connected in series in a circuit and should not appreciably change the current to be measured.
QUESTION: 13

The equivalent capacitance between the points A and B of five identical capacitors each of capacity C, will be 

Solution: The two identical branches capacitors have capacitance equal to C/2 each.
adding these in parallel will give you C/2 +C/2+C = 2C.
QUESTION: 14

The electric field intensity at a point situated 4 meters from a point charge is 200 N/C. If the distance is reduced to 2 meters, the field intensity will be

Solution:
QUESTION: 15

If an electron is brought towards an another electron, the electric potential energy of the system 

Solution:
QUESTION: 16
Two identical conductors of a copper and aluminium are placed in an identical electric field. What is the magnitude of induced charge in the aluminium ? 
Solution: As aluminum and copper are metals, their mobile electrons move under the influence of the external field until they reach the surface of the metal and collect there. External electric fields induce surface charges on metal objects that exactly cancel the field within. Since the field applied is same in both case, therefore induced charge will be the same. Since both are metals so equal amount of charge will induce on them.
QUESTION: 17

The electric field intensity at a point situated 4 meters from a point charge is 200 N/C. If the distance is reduced to 2 meters, the field intensity will be

Solution: 200=KQ/16-------equ-1
E=KQ/4-------------equ-2
on dividing1by 2
E= 800
QUESTION: 18

An electric dipole is placed at an angle of 30° with an electric field intensity 2 × 105 N/C. It experiences a torque equal to 4 N m. The charge on the dipole, if the dipole length is 2 cm, is

Solution:
QUESTION: 19

Shown in the figure is a distribution of charges. The flux of electric field due to these charges through the surface S is

Solution:

Flux flowing through a body depends on the net charge enclosed inside the surface, here net charge inside is zero so flux is also zero. And the third charge is outside so it will not effect the flux.

QUESTION: 20

Ten identical cells each of emf E and internal resistance r are connected in series to form a closed circuit. An ideal voltmeter connected across the three cells will read

Solution:

No. of cells = 10
Emf = E
Internal resistance = r
Let I = current through the ckt

Now potential (V) of across each cell will be 
V = E -Ir

We see there being no load resistance internal resistance play no effect on the observed emf
Thus the pd across 3 cells will be 
E + E + E = 3Ir = 3E

QUESTION: 21
What is the equivalent resistance between A and B in the given figure ?
Solution:
QUESTION: 22

The current in the given circuit is
 

Solution:
QUESTION: 23

An electric bulb marked 40 W and 200 V, is used in a circuit of supply voltage 100 V. Its power is

Solution:

resistance of the bulb R =  
Power = 

QUESTION: 24

A moving coil galvanometer is converted into an ammeter reading up-to 0.03 A by connecting a shunt of resistance 4r across it and into ammeter up-to 0.06 A, when a shunt of resistance r is used, what is the maximum current which can be sent through this galvanometer if no shunt is used

Solution:

For an ammeter 

and 
from Eqs. (i) and (ii)

ig = 0.02A 

QUESTION: 25

Direction : Read the following question and choose

A. If both Assertion and Reason are correct and reason is the correct explanation of assertion

B. If both Assertion and Reason are true, but Reason is not correct explanation of the Assertion

C. If Assertion is true, but the Reason is false

D. If Assertion is false, but the Reason is true

E. If both assertion and reason are false

Assertion : The capacity of conductor, under given circumstances remains constant irrespective of the charge present on it
Reason: Capacity depends on size and shape of conductor and also on the medium between the plates.

Solution:

The formula for capacity is Q=CV it does not depends on the charge present on its surface. It depends on its Size,Shape,Dielectric Medium between the plates, Arrangement of the plates, And the presence of the nearby conductors.

QUESTION: 26

Direction : Read the following question and choose

A. If both Assertion and Reason are correct and reason is the correct explanation of assertion

B. If both Assertion and Reason are true, but Reason is not correct explanation of the Assertion

C. If Assertion is true, but the Reason is false

D. If Assertion is false, but the Reason is true

E. If both assertion and reason are false

Assertion: A small metal ball is suspended in a uniform electric field with an insulated thread. If high energy X-ray beam falls on the ball, the ball will be deflected in the electric field.
Reason : X-rays emit photoelectrons and metal becomes negatively charged

Solution:
QUESTION: 27

Direction : Read the following question and choose

A. If both Assertion and Reason are correct and reason is the correct explanation of assertion

B. If both Assertion and Reason are true, but Reason is not correct explanation of the Assertion

C. If Assertion is true, but the Reason is false

D. If Assertion is false, but the Reason is true

E. If both assertion and reason are false

Assertion: If a point charge be rotated in a circle around a charge, the work done will be zero.
Reason: Work done is equal be dot product of force and displacement.

Solution:

Work done on a system of charged particle is equal to the change in electrical potential energy .Here electrical potential energy remains same as distance between the charged particle always remains equal to the radius of circle so work done in this aspect is zero

QUESTION: 28

Direction : Read the following question and choose

A. If both Assertion and Reason are correct and reason is the correct explanation of assertion

B. If both Assertion and Reason are true, but Reason is not correct explanation of the Assertion

C. If Assertion is true, but the Reason is false

D. If Assertion is false, but the Reason is true

E. If both assertion and reason are false

Assertion : The lightening conductor at the top of the high building has sharp pointed ends
Reason : The surface density increases by doing so.

Solution:

Lightning Conductor is a device used to protect a building from the effect of lightning.
A lightning conductor is made up of thick strip of metal usually of copper. The top end of the lightning conductor is pointed like sharp spike and its fixed above the highest point of building.
If lightning strikes, it will hit the top of lightning conductor  and electrical  energy passes safely through metal strip and into ground.
Usually Lightning conductors have pointed end because :
1. As Body narrows, the charge accumulated per unit surface area increases.
2. So, Spherical and pointed end objects have more density of charge.
3. So pointed end accepts more charge than round object.

QUESTION: 29

Direction : Read the following question and choose

A. If both Assertion and Reason are correct and reason is the correct explanation of assertion

B. If both Assertion and Reason are true, but Reason is not correct explanation of the Assertion

C. If Assertion is true, but the Reason is false

D. If Assertion is false, but the Reason is true

E. If both assertion and reason are false

Assertion : At any junction of a network, algebraic sum of various currents is zero
Reason : Current cannot be stored.

Solution:

The assertion is the Kirchhoff's junction rule and since current entering through the junction is equal to the current leaving through the junction, it cannot be stored. 

QUESTION: 30

Direction : Read the following question and choose

A. If both Assertion and Reason are correct and reason is the correct explanation of assertion

B. If both Assertion and Reason are true, but Reason is not correct explanation of the Assertion

C. If Assertion is true, but the Reason is false

D. If Assertion is false, but the Reason is true

E. If both assertion and reason are false

Assertion : Voltmeter is much better than a potentiometer for measuring emf of cell
Reason: A potentiometer draws no current while measuring emf of a cell

Solution:

Its D. Assertion is incorrect, Reason is correct
Explanation:-
A voltmeter cannot be used to measure the emf of a cell because a voltmeter draws some current from the cell. So, voltmeter is not better than potentiometer. While,
To measure a Emf of cell a potentiometer is used since in a potentiometer measurement no current is flowing.