#### 12th Standard Physics English Medium Free Online Test Volume 1 One Mark questions with Answer Key 2020

12th Standard

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Physics

Time : 00:25:00 Hrs
Total Marks : 25
25 x 1 = 25
1. The total electric fl ux for the following closed surface which is kept inside water

(a)

$\frac { 80q }{ { \varepsilon }_{ 0 } }$

(b)

$\frac { q }{ { 40\varepsilon }_{ 0 } }$

(c)

$\frac { q }{ { 80\varepsilon }_{ 0 } }$

(d)

$\frac { q }{ { 160\varepsilon }_{ 0 } }$

2. A thin conducting spherical shell of radius R has a charge Q which is uniformly distributed on its surface. The correct plot for electrostatic potential due to this spherical shell is

(a)

(b)

(c)

(d)

3. The relative permittivity of water is _______.

(a)

εr= 70

(b)

εr=75

(c)

εr=80

(d)

εr=85

4. What will happen if two conducting spheres are separately charged and then brought in contact?

(a)

Total charge on the two spheres is conserved

(b)

The total energy is conserved

(c)

Both charge and energy are conserved

(d)

The final potential is the mean of the original potentials.

5. A non-conducting material which has no free electrons is called

(a)

capacitor

(b)

Dielectric

(c)

conductor

(d)

Inductor

6. A charge q is placed at the centre of a cubical box of side with top open. The flux of electric field through the surface of the cubical box is

(a)

Zero

(b)

$\frac { q }{ { \varepsilon }_{ 0 } }$

(c)

$\frac { q }{ 6{ \varepsilon }_{ 0 } }$

(d)

$\\ \frac { 5q }{ 6{ \varepsilon }_{ 0 } }$

7. Two point charges +q and -q are placed at points A and B respectively separated by a small distance. The electric field intensity at the midpoint O of AB :

(a)

is zero

(b)

acts along AB

(c)

acts along BA

(d)

acts perpendicular to AB

8. A toaster operating at 240 V has a resistance of 120 Ω. Th e power is

(a)

400 W

(b)

2 W

(c)

480 W

(d)

240 W

9. What is the current out of the battery?

(a)

1A

(b)

2A

(c)

3A

(d)

4A

10. A potential difference is applied an the ends of a metallic wire. If the potential difference is doubled, the drift velocity

(a)

will be doubled

(b)

will be halved

(c)

(d)

will remain unchanged

11. The thermistors are usually made of

(a)

metals with low temperature coefficient of resistivity

(b)

metals with high temperature coefficient of resistivity

(c)

metal oxides with high temperature coefficient of resistivity

(d)

semi conducting materials with low temperature coefficient of resistivity

12. A resistance of a metal wire of length AB is 2$\Omega$. Another wire of length PQ of the same metal with twice the diameter of the wire AB is found to have the same resistance of2$\Omega$. What is the length of PQ?

(a)

4 AB

(b)

2 AB

(c)

1AB

(d)

6 AB

13. Two identical coils, each with N turns and radius R are placed coaxially at a distance R as shown in the fi gure. If I is the current passing through the loops in the same direction, then the magnetic field at a point P which is at exactly at$\frac { R }{ 2 }$ distance between two coils is

(a)

$\frac { 8N{ \mu }_{ ° }I }{ \sqrt { 5 } R }$

(b)

$\frac { 8N{ \mu }_{ ° }I }{ { 5 }^{ \frac { 3 }{ 2 } }R }$

(c)

$\frac { 8N{ \mu }_{ ° }I }{ { 5 }R }$

(d)

$\frac { 4N{ \mu }_{ ° }I }{ \sqrt { 5 } R }$

14. An electron of mass 0.90 x 10-30kg under the action of a magnetic field moves in a circle of 2cm radius at a speed of 3 x 106 m/s if a proton of mass 1.8 x 10-27 kg was to move in a circle of the same radius in the same magnetic field, then its speed will be

(a)

3.0 x 106 m/s

(b)

1.5 x 103 m/s

(c)

6.0 x 104 m/s

(d)

cannot be estimated from the same data

15. To convert a galvanometer into an ammeter we connect which one of the following to the galvanometer?

(a)

a low resistance in series

(b)

a high resistance in series

(c)

a low resistance in parallel

(d)

a high resistance in parallel

16. Magnetic Lorentz force makes a moving charged particle to follow a _______

(a)

linear path

(b)

parabolic path

(c)

elliptical path

(d)

circular path

17. No current flows between two charged particles when connected if they have same ______

(a)

capcity

(b)

potential

(c)

charge

(d)

none of these

18. An electron moves on a straight line path XY as shown in the figure. The coil abcd is adjacent to the path of the electron. What will be the direction of current, if any, induced in the coil?

(a)

The current will reverse its direction as the electron goes past the coil

(b)

No current will be induced

(c)

abcd

(d)

19. The self-inductance of a straight conductor is

(a)

zero

(b)

infinity

(c)

very large

(d)

very small

20. In a transformer, eddy current loss is minimized by using

(a)

(b)

(c)

shell type core

(d)

thick copper wire

21. The reactance of a capacitor is,

(a)

Xc = Cω

(b)

Xc$\frac{1}{Cω}$

(c)

Xc$\frac{C}{ω}$

(d)

Xc$\frac{ω}{C}$

22. Consider an oscillator which has a charged particle and oscillates about its mean position with a frequency of 300 MHz. Th e wavelength of electromagnetic waves produced by this oscillator is

(a)

1 m

(b)

10 m

(c)

100 m

(d)

1000 m

23. In vacuum speed of light depends upon

(a)

colour

(b)

wavelength

(c)

frequency

(d)

none of the above

24. Which one of the following is not an electromagnetic waves?

(a)

Gamma rays

(b)

X-rays

(c)

Beta rays

(d)

Microwaves

25. We can make long distance photographs using _________.

(a)

(b)

visible light

(c)

X-rays

(d)

IR rays