Physics M.C.Q (1 Marks)

1. Electrostatic energy.

4. 32

Explanation:

The required voltage is 1000v and the capacitors are parallel as 250v.

So number of capacitors required will be 4  i.e250 × 4 = 1000 in series.

Now example of four capacitor in series will be equal 2μf (micro farade) but the equivalent capacitance required is given as 16μf so there must be 8 series of parallel arrange capacitors each of capacitor 2 micro farad hence total number of capacitor = 4 × 8 = 32

2. Electric potential.

Explanation:

The electric potential is the electric potential energy per unit charge.

2. An electrical impulse associated with the functioning of organs and tissues of human body.

Explanation:

The heart generates by itself an electrical activity which is transmitted through all the organ and produces its contraction. The Electrocardiogram is no other than the graphical representation of this electrical activity.

2. Volt.

2. Sum of all the individual capacitors in parallel.

Explanation:

The equivalent capacitance of the capacitors connected in parallel is given by sum of their individual capacitances, that is if there are n capacitors in parallel the total capacitance is given by, C = C₁ + C₂ + C₃ + C₄ + ….. + C_n.

3. Depends on the maximum electric field.

Explanation:

The maximum energy that can be desirably stored in a capacitor is depends on the maximum electric field that the dielectric can withstand without breaking down. Therefore, capacitors of the same type have about the same maximum energy density, i.e. joules of energy per cubic meter.

1. A will be at higher potential.

Explanation:

Point A have positive charge.

More is the positive charge, more will be the potential. So, A will be at higher potential.

3. S₁ is true, S₂ is also true and S₁ is the cause of S_2.

4. Capacitor.

4. Charge.

1. [M1 L2 T-3 A-1]

3. Remains constant

Explanation:

As the battery remains connected across the capacitor, so the potential difference remains constant at V₀ even after the introduction of the dielectric slab. In this way, dielectric has an effect on potential difference.

4. Electric potential.

1. unchanged

Explanation:

As no cell is connected to the capacitor, the charge will remain constant.

1. Charge on C₁ gets redistributed such that V₁ = V₂.

4. Charge on C₁ gets redistributed such that Q₁' + Q₂' = Q.

Initially key K₁ is closed and key K₂ is open, the capacitor C₁ is charged by battery and capacitor C₂ is still uncharged. Now K₁ is opened and K₂ is closed, the capacitors C₁ and C₂ both are connected in parallel. The charge stored by capacitor C₁, gets redistributed between C₁ and C₂ till their potentials become same, i.e., V₂ = V₁.

By law of conservation of charge, the charge stored in capacitor Cx is equal to sum of charges on capacitors C₁ and C₂ when K₁ is opened and K₂ is closed, i.e., Q'₁ + Q'₂ = Q.

2. Area of the plate is increased.

4. remains same throughout the conductor.

Explanation:

Given that some charge is given to a conductor then the whole charge is distributed over its surface only. Inside of conductor, electric field is zero whereas potential is same as on the surface. Hence, throughout the conductor, potential is same i.e, the whole conductor is equipotential.

2. Decreased, proportional to 1/ 2.

2. Current.

3. They can be charged equally (maximum).

2. 10-9.

2. 500 V

Explanation:

The total work done = energy transferred.

So, we might see the equation energy = voltage x charge, E = V × Q, written as,

work = voltage x charge, W = V × Q.

In this case, the charge is 4 mC, that is, 0.004 C and work done is 2J.

1. NH₃

Explanation:

NH₃ is a molecule in which the centre of mass of positive and negative charges does not collide with each other and is called a polar molecule. They have a permanent dipole moment. They have unsymmetrical shapes.

3. A spherical surface at a distance of 1km from the surface of the earth with its centre at centre of earth.

Explanation:

The potential is seen to be a constant on a sphere at all points.

4. Both a and b.

1. Electric potential.

Explanation:

Electric potential is defined as the amount of work done to bring a unit positive charge from an infinite distance to a particular point of an electric field. The total energy of that point charge means the sum of kinetic energy and potential energy which is not the same as the potential energy if the particle is in motion.

1. Equipotential

Explanation:

Electric field at any point is equal to the negative of the potential gradient. But inside a conductor, the electric field is zero. Hence, the electric potential is constant throughout the volume of a conductor and has the same value on its surface. Thus the surface of a conductor is equipotential.

4. E_q​ is zero, if X is metallic.

Explanation:

There is no effect of the metal on the external electric field(thus A is incorrect) while the dielectric reduces the net electric field outside. The dielectric produces an electric field inside it due to the induced charges which is opposite to the external field. Thus EQ​ is reduced and B and C are also incorrect.(Note that E_P​ is not the external field). Now as the electric field inside the conductor is zero, the field E_p​ is zero if X is a metallic.

2. Spherical

Explanation:

We know that electric field lines cross the equipotential surfaces perpendicularly. Electric field lines are generated radially from a positive point charge. Therefore, for holding both the conditions, the equipotential surfaces must be spherical.

3. Infinite.

2. C = C₁ + C₂

1. The present state of the configuration.

4. zero

Explanation:

Every condenser is made with two plates. The charge on one plate is +Q and other is −Q.

Thus total charge of condenser is Qt​ = +Q - Q = 0

3. Work done along all the paths are zero.

Explanation:

As the charge q is situated at the center of the circle ABCDE, therefore the circle is an equipotential surface. That means all the points on the circle i.e. A, B, C, D, and E have the same potential. Therefore, work done to bring the charge from A to any point on the circle is zero always.

2. 10-6

1. 0.8J

Explanation:

Work done = potential × charge by definition. We know that the potential of a point is the amount of work done to bring a unit charge from infinity to a certain point. Therefore, work done W = q × V = 4 × 10^-3 × 200J = 0.8J. The work done is positive in this case.

3. Electrostatic shielding

Explanation:

Electrostatic shielding is a phenomenon seen when a Faraday cage is used to block the effects of an electric field.

3. Zero

Explanation:

Any point on the perpendicular bisector is equidistant from both the charges of the dipole. Therefore, the electric potential at that point is equal and opposite due to the two different charges. Therefore, the total electric potential at that point is zero.

1. Work is done on the body by an external agent.

Explanation:

To move a body against some force, work is to be done on the body. In this case, an external force is to be applied on the body to move it i.e. an external work is to be done. As we are moving the body against the Coulomb’s force, hence no work is done on the body by the electric field.

2. 4V

Explanation:

Total charged is conserved in the condenser. Here the potential difference on the condenser is equal to the emf of battery. When dielectric is inserted between the plates the charge will maintain the constant potential in the capacitor. Thus, the potential difference on the condenser is 4V

2. Increases

Explanation:

As the dielectric slab is introduced there is some charge distribution in the slab and because of this the electric field between the two plates is decreased, due to which the capacitor can hold more charge. Thus, the capacity to hold charge of the capacitor is increased.

3. Zero

Explanation:

Work done is given difference in potentials. In an equipotential surface, all points will have same potential. Thus work done is zero

4. remains constant from centre to the surface.

1. Equipotential lines are always perpendicular to the electric field.

Explanation:

There is no potential gradient along any direction parallel to the surface, and no electric field is parallel with the surface, This means electric field are always at right angle to the equipotential surface.