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

12th Standard

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Physics

Time : 00:25:00 Hrs
Total Marks : 25
25 x 1 = 25
1. A parallel plate capacitor stores a charge Q at a voltage V. Suppose the area of the parallel plate capacitor and the distance between the plates are each doubled then which is the quantity that will change?

(a)

Capacitance

(b)

Charge

(c)

Voltage

(d)

Energy density

2. The value of constant 'K' in coulomb law is

(a)

0.9 x 109 Nm2 C2

(b)

9 x 10-9 Nm2C2

(c)

9 x 109 Nm-2 C-2

(d)

9 x 109 Nm2 C-2

3. Four plates each of area 'N. and inferplate separation 'd' are placed as shown in figure. The two inner plates are connected to the point 'B' and outer to point 'A'. What is equivalent capacitance?

(a)

$\frac { { \varepsilon }_{ 0 }A }{ d } \\$

(b)

$\frac { {2 \varepsilon }_{ 0 }A }{ d } \\$

(c)

$\frac { {3 \varepsilon }_{ 0 }A }{ d } \\$

(d)

$\frac { {4 \varepsilon }_{ 0 }A }{ d } \\$

4. A piece of copper and another of germanium are cooled from room temperature to 80 K. The resistance of

(a)

each of them increases

(b)

each of them decreases

(c)

copper increases and germanium decreases

(d)

copper decreases and germanium increases

5. Which of the following has negative temperature coefficient of resistance?

(a)

copper

(b)

tungsten

(c)

carbon

(d)

silver

6. A non-conducting charged ring of charge q, mass m and radius r is rotated with constant angular speed ω. Find the ratio of its magnetic moment with angular momentum is

(a)

$\\ \frac { q }{ m }$

(b)

$\\ \frac { 2q }{ m }$

(c)

$\\ \frac { q }{ 2m }$

(d)

$\\ \frac { q }{ 4m }$

7. The direction of magnetic field close to a straight conductor carrying current will be

(a)

along the length of the conductor

(b)

(c)

circular in a plane perpendicular to the conductor

(d)

helical

8. 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

9. The phase difference between VL and Vc is _________________

(a)

(b)

π/2

(c)

π/4

(d)

π

10. A rod of length 10 cm lies along the principal axis of a concave mirror of focal length 10 cm in such a way that its end closer to the pole is 20 cm away from the mirror. The length of the image is,

(a)

2.5 cm

(b)

5cm

(c)

10 cm

(d)

15cm

11. Two plane mirrors are parallel to each other an spaced 20cm apart. An object is kept in between them at lScm from A. out of the following at which point on image is not formed in mirror A (distance measured from mirror A)

(a)

15 cm

(b)

25 cm

(c)

45 cm

(d)

55 cm

12. In an electron microscope, the electrons are accelerated by a voltage of 14 kV. If the voltage is changed to 224 kV, then the de Broglie wavelength associated with the electrons would

(a)

increase by 2 times

(b)

decrease by 2 times

(c)

decrease by 4 times

(d)

increase by 4 times

13. Light exhibits _______ duality.

(a)

particle-wave

(b)

solid-liquid

(c)

liquid-gas

(d)

gas-plasma

14. Energy of each photon is ______

(a)

$\frac{2}{3}$ hv

(b)

3 hv

(c)

2 hv

(d)

hv

15. Photoelectric cells are of _______ types.

(a)

two

(b)

three

(c)

four

(d)

five

16. In burglar-alarm, ________ is continuously made to fall' on the photo cell.

(a)

(b)

UV rays

(c)

visible light

(d)

$\gamma$-rays

17. Wavelength of X-rays is ______ the wavelength of visible light

(a)

smaller than

(b)

greater than

(c)

negligible when compared to

(d)

equal to

18. The ratio between the first three orbits of hydrogen atom is

(a)

1:2:3

(b)

2:4:6

(c)

1:4:9

(d)

1:3:5

19. In a discharge tube, the source of positive rays is

(a)

cathode

(b)

anode

(c)

gas atoms present in the discharge tube

(d)

fluorescent screen

20. The ground-state energy of hydrogen atom is ____________ eV

(a)

-13.6

(b)

-18.7

(c)

18.6

(d)

$\frac{1}{13.6}$

21. The specific characteristic of a common emitter amplifier is

(a)

High input resistance

(b)

Low power gain

(c)

Signal phase reversal

(d)

Low current gain

22. In a p-n junction diode

(a)

the current in the reverse biased condition is generally very small

(b)

the current in the reverse biased condition is small but the forward biased current is independent of the biased voltage

(c)

the reverse biased current is strongly dependent on the applied bias voltage.

(d)

the forward biased current is very small in comparison to reverse biased current

23. In a television, the picture signals are _________ modulated.

(a)

amplitude

(b)

frequency

(c)

phase

(d)

pulse-code

24. The transmitter in a RADAR is a high power ________.

(a)

cyclotron oscillator

(b)

magnetron oscillator

(c)

Hartley oscillator

(d)

simple harmonic oscillator

25. __________ Scanning Electron Micrograph (SEM) showing the nano structures on the surface of a leaf from a lotus plant

(a)

Parrot fish

(b)

Morpho butterfly

(c)

Lotus leaf surface

(d)

Peacock feathers