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12th Standard Physics English Medium Free Online Test 1 mark questions 2020 - Part Five

12th Standard EM

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Physics

Time : 00:25:00 Hrs
Total Marks : 25
Answer all the questions
25 x 1 = 25
1. Rank the electrostatic potential energies for the given system of charges in increasing order.

(a)

1 = 4 < 2 < 3

(b)

2 = 4 < 3 < 1

(c)

2 = 3 < 1 < 4

(d)

3 < 1 < 2 < 4

2. A positively charged body 'A' has been brought near a brass cylinder 'B' mounted on a glass stand as shown in the figure. The potential of 'B' will be

(a)

zero

(b)

Negative

(c)

positive

(d)

Infinite

3. What physical quantities may X and Y represent? [Y represents the first mentioned quantity].

(a)

K.E - velocity of a particle

(b)

pressure - temperature of a given gas (constant volume)

(c)

capacitance - charge to give a constant potential

(d)

potential - capacitance to give a constant charge

4. Electrostatics deals with the _________

(a)

charges in motion

(b)

static electric charges

(c)

charges through conductors

(d)

accelerated charges

5. In India electricity is supplied for domestic use at 220 V. It is supplied at 110 V in USA. If the resistance of a 60W bulb for use in India is R, the resistance of a 60W bulb for use in USA will be

(a)

R

(b)

2R

(c)

$\frac{R}{4}$

(d)

$\frac{R}{2}$

6. Four resistances are connected to a 5V battery of negligible internal resistance as shown what is the potential across $2\Omega$?

(a)

0.5 V

(b)

1:5 V

(c)

1.0 V

(d)

1.0 V

7. An ideal cell is connected to a capacitor through a voltmeter. The reading V of the voltmeter is plotted against time. Which of the following best represents the resulting curve?

(a)

(b)

(c)

(d)

8. Calculate the mobility of a free electron in an electric field of 10+2N/C.

(a)

10-4m2V-1s-1

(b)

10-5m2V-1s-1

(c)

10-3m2V-1s-1

(d)

105m2V-1s-1

9. A flat dielectric disc of radius R carries an excess charge on its surface. The surface charge density is σ. The disc rotates about an axis perpendicular to its plane passing through the center with angular velocity ω. Find the magnitude of the torque on the disc if it is placed in a uniform magnetic field whose strength is B which is directed perpendicular to the axis of rotation

(a)

$\frac { 1 }{ 4 } \sigma \omega \pi BR$

(b)

$\frac { 1 }{ 4 } \sigma \omega \pi B{ R }^{ 2 }$

(c)

$\frac { 1 }{ 4 } \sigma \omega \pi B{ R }^{ 3 }$

(d)

$\frac { 1 }{ 4 } \sigma \omega \pi B{ R }^{ 4 }$

10. 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

11. When the number of turns (n) in a galvanometer is doubled, current sensitivity

(a)

remains constant

(b)

decreases twice

(c)

increases twice

(d)

increases four times

12. A galvanometer can be converted into a voltmeter by connecting

(a)

a low resistance in parallel to it

(b)

a high resistance in parallel to it

(c)

a low resistance in series with it

(d)

a high resistance in series with it

13. In a series resonant RLC circuit, the voltage across 100 Ω resistor is 40 V. The resonant frequency ω is 250 rad/s. If the value of C is 4 μF, then the voltage across L is

(a)

600 V

(b)

4000 V

(c)

400 V

(d)

1 V

14. Quality factor = ?

(a)

$\frac{output \ power}{input \ power}$

(b)

$\frac{output \ current}{input \ current}$

(c)

$\frac{voltage \ across \ L (or) \ C}{applied \ voltage}$

(d)

$\frac{random \ frequency}{resonant \ frequency}$

15. The rays used in weather forecasting is ___________.

(a)

I-R rays

(b)

U-V rays

(c)

X - rays

(d)

μ-Waves

16. An object is placed in front of a convex mirror of focal length of f and the maximum and minimum distance of an object from the mirror such that the image formed is real and magnified.

(a)

2f and c

(b)

c and $\infty$

(c)

f and O

(d)

None of these

17. A ray of light is incidenting normally on a .plane mirror. The angle of reflection will be

(a)

(b)

90°

(c)

will not be reflected

(d)

None of these

18. Radius of curvature of concave mirror is 40 cm and the size of image is twice as that of object, then the object distance is

(a)

60 cm

(b)

20 cm

(c)

40 cm

(d)

30 cm

19. A particle of mass 3 × 10–6 g has the same wavelength as an electron moving with a velocity 6 10 × 6m s−1. The velocity of the particle is

(a)

1.82x10-18ms-1

(b)

9x10-2ms-1

(c)

3x10-15ms-1

(d)

1.82x10-15ms-1

20. The photo current in an experiment on photoelectric effect increases if

(a)

the intensity of the source is increased

(b)

the exposure time is increased

(c)

the intensity of the source is decreased

(d)

the exposure time is decreased

21. Einstein's photoelectric equation is an equation of a _______

(a)

circle

(b)

sphere

(c)

straight line

(d)

ellipse

22. For a transistor, in a common base configuration the alternating current gain is given by:

(a)

${ \left[ \frac { \triangle { I }_{ C } }{ \triangle { I }_{ B } } \right] }_{ { V }_{ c }=constant }$

(b)

${ \left[ \frac { \triangle { I }_{ B } }{ \triangle { I }_{ C } } \right] }_{ { V }_{ c }=constant }$

(c)

${ \left[ \frac { \triangle { I }_{ C } }{ \triangle { I }_{ E } } \right] }_{ { V }_{ c }=constant }$

(d)

${ \left[ \frac { \triangle { I }_{ E } }{ \triangle { I }_{ C } } \right] }_{ { V }_{ c }=constant }$

23. How many AND gates are required to form NAND gate?

(a)

1

(b)

2

(c)

3

(d)

4

24. For long distance, shortwave radio broadcasting __________ wave is used.

(a)

ground

(b)

ionospheric

(c)

sky

(d)

direct

25. Messages cannot be transmitted over long distances in _________ transmission.

(a)

FM

(b)

PM

(c)

AM

(d)

PCM