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

12th Standard

Reg.No. :
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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. The relative permittivity of water is _______.

(a)

εr= 70

(b)

εr=75

(c)

εr=80

(d)

εr=85

3. An isolated metal sphere of radius 'r' is given a charge' q'. The potential energy of the sphere is

(a)

$\frac { { q }^{ 2 } }{ 4\pi { \varepsilon }_{ 0 }r }$

(b)

$\frac { { q }^{ } }{ 4\pi { \varepsilon }_{ 0 }r }$

(c)

$\frac { { q }^{ } }{ 8\pi { \varepsilon }_{ 0 }r }$

(d)

$\frac { { q }^{ 2 } }{ 8\pi { \varepsilon }_{ 0 }r }$

4. The direction of electric field at a point the equatorial line due to an electric dipole is

(a)

along the equatorial line towards the dipole.

(b)

along the equatorial line away from the dipole

(c)

parallel to the axis of the dipole and opposite to the direction of dipole moment

(d)

parallel to the axis of the dipole and in the direction of dipole moment.

5. When three capacitors are joined in series, the total capacitance is

(a)

Equal to the sum of the capacitance

(b)

Greater than the value of the maximum capacitance

(c)

Less than the value of the mininim capacitance

(d)

none of the above

6. By using law of conservation of electric charge balance the following equations:
92U238 90Th234 ________.

(a)

2He4

(b)

1H3

(c)

1H2

(d)

1H1

7. Electric lines of force ________.

(a)

intersect each other

(b)

never intersect

(c)

intersect at infinity

(d)

are always parallel

8. The torque (-ፒ) experienced by an electric dipole placed in a uniform electric field (E) at an angle θ with the field is

(a)

pEcosθ

(b)

pE cosθ

(c)

pE sinθ

(d)

2pE sinθ

9. 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

10. The temperature co-efficient of resistance for alloys is

(a)

low

(b)

very low

(c)

high

(d)

very high

11. Which of the following is an identical.

(a)

germanium, silicon

(b)

silver, wood

(c)

aluminum, constantan

(d)

bakelite, iron

12. conductivity is the reciprocal of

(a)

resistance

(b)

specific resistance

(c)

conductance

(d)

potential difference

13. Which of the following is not related to joule's law of heating?

(a)

$H=VIt$

(b)

$H={ I }^{ 2 }Rt$

(c)

$H=\cfrac { { V }^{ 2 }t }{ R }$

(d)

$H=\cfrac { { I }^{ 2 }R }{ t }$

14. For which of the following substances, resistance decreases with temperature?

(a)

copper

(b)

platinum

(c)

mercury

(d)

carbon

15. Th ree wires of equal lengths are bent in the form of loops. One of the loops is circle, another is a semi-circle and the third one is a square. Th ey are placed in a uniform magnetic fi eld and same electric current is passed through them. Which of the following loop confi guration will experience greater torque ?

(a)

circle

(b)

semi-circle

(c)

square

(d)

all of them

16. In which of the following pairs of metals of the thermocouple, the emf is maximum?

(a)

Fe-Cu

(b)

Cu-Zn

(c)

Pt-Ag

(d)

Sb-Bi

17. The orbital magnetic moment of an electron in the second orbit (n = 2) is

(a)

18.54 x 10-24 Am2

(b)

18.54 x 10-34 Am2

(c)

19.44 x 10-34 Am2

(d)

19.44 x 10-24 Am2

18. In an electrical circuit, R, L, C and AC voltage source are all connected in series. When L is removed from the circuit, the phase difference between the voltage and current in the circuit is $\frac{\pi}{3}$. Instead, if C is removed from the circuit, the phase difference is again  $\frac{\pi}{3}$.  The power factor of the circuit is

(a)

1/2

(b)

1/$\sqrt2$

(c)

1

(d)

$\sqrt3$/2

19. The self-inductance of a straight conductor is

(a)

zero

(b)

infinity

(c)

very large

(d)

very small

20. The generator rule is

(a)

Fleming's left hand rule

(b)

Fleming's right hand rule

(c)

Maxwell's right hand cork screw rule

(d)

Right hand palm rule

21. During the propagation of electromagnetic waves in a medium

(a)

electric energy density is double of the magnetic energy density

(b)

electric energy density is half of the magnetic energy density

(c)

electric energy density is equal to the magnetic energy density

(d)

both electric and magnetic energy densities are zero

22. The existence of E.M. waves was confirmed experimentally by

(a)

Hertz

(b)

Maxwell

(c)

Huygens

(d)

Planck

23. The wavelength of electromagnetic wave produced by Hertz experiment was

(a)

6mm

(b)

60m

(c)

6000 mm

(d)

60 cm

24. Electric filament lamp gives rise to

(a)

line spectrum

(b)

continuous spectrum

(c)

continuous absorption spectrum

(d)

line absorption spectrum

25. ________ radiations are used to study atomic structure.

(a)

UV

(b)

IR

(c)

X-rays

(d)

Gamma