Free Printable Physics Unit 6 Test

1.

Two small spheres each carrying a charge q are placed r metre apart. If one of the spheres is taken around the other one in a circular path of radius r, the work done will be equal to

a)

Force between them × r

b)

Force between them × 2πr

c)

Force between them/2πr

d)

Zero

2.

A hollow metal sphere of radius 5 cm is charged so that the potential on its surface is 10 V. The potential at the centre of the sphere is

a)

0 V

b)

10 V

c)

Same as at point 5 cm away from the surface

d)

Same as at point 25 cm away from the surface

3.

A charge Q placed at the centre of two charges + q and + q. the system is in equilibrium then net force experienced by Q.

a)

Zero

b)

F

c)

At equilibrium, net force will be zero

d)

F/2

4.

Two positive point charges q₁=16.0μC and q₂ = 4.0 $\mu$ C are separated by a distance of 3.0 m, as shown in Fig. Find the spot on the line joining the two charges where electric field is zero.

a)

1m

b)

-1m

c)

2m

d)

None of these

5.

Two conducting spheres of radius r1 and r2

are at the same potential. The ratio of their charges is:

a)

$\left(\frac{r^{\frac{2}{1}}}{r^{\frac{2}{2}}}\right)$

b)

$\left(\frac{r^{\frac{2}{2}}}{r^{\frac{2}{1}}}\right)$

c)

$\left(\frac{r_1}{r_2}\right)$

d)

$\left(\frac{r_2}{r_1}\right)$

6.

For a set of oppositely charged, infinite parallel plates, what is true about the electric field inside and outside the plates?

a)

The electric field decreases as you move from the positive to the negative plate and is a non-zero constant outside.

b)

The electric field decreases as you move from the positive to the negative plate and is non-zero constant outside.

c)

The electric field is a non-zero constant within the plates and zero outside

d)

The electric field is zero within the plates and a non-zero constant outside

7.

Two protons A and B are placed is between the two plates of a parallel plate capacitor charged to a potential difference V as shown in figure. The force on two protons are F_A and F_B ; then

a)

F_A > F_B

b)

F_A < F_B

c)

F_A = F_B

d)

Nothing can be predicted

8.

The dielectric constant of metals is

a)

One

b)

Zero

c)

Infinity

d)

Greater than one

9.

The capacity of a parallel plate condenser is 5μF. When a glass plate is placed between the plates of the conductor, its potential becomes 1/8th of the original value. The value of dielectric constant will be

a)

1.6

b)

5

c)

8

d)

40

10.

The diagram shows four pairs of large parallel conducting plates. The value of the electric potential is given for each plate. Rank the pairs according to the magnitude of the electric field between the plates, least to greatest.

a)

1, 2, 3, 4

b)

4, 3, 2, 1

c)

2, 3, 1, 4

d)

2, 4, 1, 3

11.

Field free region is obtained

a)

Between equal and opposite charges

b)

Surface of charged sphere

c)

Between equal and same charges

d)

None

12.

A hollow metal sphere of radius 5cm is charged such that the potential on its surface is 10V. The potential at a distance of 2cm from centre of sphere is

a)

Zero

b)

10 V

c)

4 V

d)

10/3 V

13.

If 4 × 10²⁰ eV of energy in required to move a charge of 1C between two points, the P. D between the points is

a)

4 × 10²⁰ V

b)

64 × 18²⁰ V

c)

64 × 19¹⁹ V

d)

64 V

14.

A gold nucleus (radius r) is represented by the symbol $_{79}^{197}Au$ taking as the elementary charge. What is the electric field strength at the surface of an isolated gold nucleus?

a)

Zero

b)

$\frac{79e}{4\pi\in_or^2}$

c)

$\frac{179e}{4\pi\in_or^2}$

d)

$\frac{79e^2}{4\pi\in_or^2}$

15.

The electric potential due to the nucleus of the hydrogen atom at a distance of 5.3 x 10^–11 m is 27.2 V. What is the potential due to the helium nucleus at the same distance?

a)

27.2V

b)

54.4 V

c)

13.6 V

d)

27.2 V

16.

The coulombs force between two-point charges is F. If magnitude of each charge is doubled and distance between charges is halved, the forces between them becomes

a)

F

b)

8F

c)

4F

d)

16F

17.

A capacitor charges and discharges:

a)

Rapidly

b)

Linearly

c)

Exponentially

d)

Logarithmically

18.

Two opposite point charges each of magnitude 1C are separated by a distance of 2m. The electric potential at middle point between them is

a)

1V

b)

0.5V

c)

0.85V

d)

0V

19.

Three capacitors C1, C2 and C3 are connected in parallel as in the Fig. The equivalent capacitance will be

a)

8μF

b)

0.8μF

c)

1μF

d)

16μF

20.

The net charge on a capacitor (each plate having magnitude of charge q) is:

a)

Infinity

b)

2q

c)

$\frac{q}{2}$

d)

Zero

21.

From the following figure:

The time constant of the above circuit is

a)

4.0 ms

b)

2.5 sec

c)

25 ms

d)

4.0 sec

22.

Three charges are placed at the vertices of an equilateral triangle of side ‘a’ as shown in Fig. The force experienced by the charge placed at the vertex A in a direction normal to BC is:

a)

$Q^2\left(4\pi\in_0a^2\right)$

b)

Zero

c)

$-Q^2\left(4\pi\in_0a^2\right)$

d)

$Q^2\left(2\pi\in_0a^2\right)$

23.

The coulomb force between an electron and a proton placed at a distance of 3.2 cm is:

a)

$5.2\times10^{-25}N$

repulsive

b)

$9.1\times10^{-25}N$ attractive

c)

$1.5\times10^{-25}N$

repulsive

d)

$2.2\times10^{-25}N$ attractive

24.

The electric field produced by a point charge q=-8×10^-6 C (placed at origin) at a point 3 m from origin on the y-axis is:

a)

$(-4\times10^3jˆ)NC^{-1}$

b)

$(-8\times10^3jˆ)NC^{-1}$

c)

$(-6\times10^3jˆ)NC^{-1}$

d)

$(-9\times10^3kˆ)NC^{-1}$

25.

A capacitor which has a capacitance of 100 $\mu$ F will:

a)

Be fully charged in 1 second by a current of 1 $\mu$ A

b)

Store 0.1 mC of charge at a potential difference of 1 volt

c)

Gain 1 joule of energy when 1 coulomb of charge is stored on it

d)

Discharge in 1 second when connected across a resistor of resistance 1 ohm

26.

The electric field produced by a point charge varies with distance from point charge as:

a)

b)

c)

d)

27.

Compare the electrons accelerated through a certain potential difference and protons accelerated through the same potential difference. If initial velocities are negligible, then the emergent:

a)

Electrons have smaller K.E

b)

Protons have larger velocity

c)

Electrons have larger momentum

d)

Protons have larger momentum

28.

For a uniformly charged spherical shell of radius “r”, which one of the following graphs shows the variation of the potential with distance “x” from the centre of the shell?

a)

b)

c)

d)

29.

If potential difference is applied between the ends of the conductor, then:

a)

Electric lines of force are not present inside the conductor

b)

Electric lines of force must be present inside the conductor

c)

Electric field inside the conductor is zero

d)

Electric field inside the conductor is infinite

30.

In the midway between two equal and similar charges, a third equal and similar charge is placed. Then the third charge:

a)

Experiences maximum net force.

b)

Experiences no net force

c)

Experiences net force perpendicular to axial line

d)

Experiences net force inclined at 45° to axial line

31.

A point charge at a distance “x” from another point charge experiences a force of attraction. Which one of following graphs shows how the force is related to “x”.

a)

b)

c)

d)

32.

In bringing an a-particle towards a proton, the electrostatic potential energy of the system :

a)

Becomes zero

b)

Decreases

c)

Remains the same

d)

Increases

33.

Two protons are placed near a point charge “q” at point “N” and “O” as shown in diagram.

Which of following describe the force on both protons correctly?

a)

A

b)

B

c)

C

d)

D

34.

A sphere of charge “+Q” is fixed in position. A smaller sphere of charge “+q” is placed near the larger sphere and released from rest. The smaller sphere will move away from larger sphere with velocity and slope of velocity time graph?

a)

Decreasing, Increasing

b)

Increasing, increasing

c)

Increasing, Decreasing

d)

Increasing, Constant

35.

When a charge +q is moving perpendicular to electric field, the force experienced is:

a)

qE and along the field

b)

qE and opposite to the field

c)

qE and perpendicular to the field

d)

Zero

36.

A parallel plate capacitor has a capacitance of 25 pF in air and 112.5 pF when immersed in oil. The dielectric constant of the oil is:

a)

4.5

b)

2.9

c)

3.7

d)

5.3

37.

For which of the following graph the area represents energy stored in capacitor?

a)

b)

c)

d)

38.

Electric field lines between plates of a charged parallel plate capacitor are:

a)

Unequally Spaced

b)

Curved

c)

Equally spaced

d)

Any of these

39.

The ratio of instantaneous charge and maximum charge on plates of capacitor at t=RC is (during discharging)

a)

36.8%

b)

63.2%

c)

92.5%

d)

87.3%

40.

A capacitor is charged with a battery and then it is disconnected. A slab of the dielectric is now inserted between the plates then:

a)

The charge in the plates reduces and potential difference increases

b)

Potential difference between the plates increases, stored energy decreases and charge remains the same

c)

Potential difference between the plates decreases, stored energy decreases and charge remains unchanged

d)

None of these

Physics Unit 6 Test

Total questions: 40

Worksheet time: 3600secs

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