#### 12th Standard Physics Current Electricity English Medium Free Online Test One Mark questions with Answer Key 2020 - 2021

12th Standard

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Physics

Time : 00:20:00 Hrs
Total Marks : 20
20 x 1 = 20
1. A wire of resistance 2 ohms per meter is bent to form a circle of radius 1m. The equivalent resistance between its two diametrically opposite points, A and B as shown in the figure is ____________

(a)

$\pi \Omega$

(b)

$\frac{\pi}{2}\Omega$

(c)

2$\pi \Omega$

(d)

$\frac{\pi}{4}\Omega$

2. A carbon resistor of (47 ± 4.7 ) k Ω to be marked with rings of different colours for its identification. The colour code sequence will be

(a)

Yellow–Green–Violet –Gold

(b)

Yellow – Violet – Orange – Silver

(c)

Violet – Yellow – Orange – Silver

(d)

Green – Orange – Violet - Gold

3. There is a current of 1.0 A in the circuit shown below. What is the resistance of P ?

(a)

1.5 Ω

(b)

2.5 Ω

(c)

3.5 Ω

(d)

4.5 Ω

4. The temperature coefficient of resistance of a wire is 0.00125 per °C. At 300 K, its resistance is 1 Ω. The resistance of the wire will be 2 Ω at ______________

(a)

1154 K

(b)

1100 K

(c)

1400 K

(d)

1127 K

5. The electrical resistivity of a thin copper wire and a thick copper wire are respectively ${ P }_{ 1 }\Omega$ m and ${ P }_{ 2 }\Omega$ m Then_____________.

(a)

${ P }_{ 1 }>{ P }_{ 2 }$

(b)

${ P }_{ 2 }>{ P }_{ 1 }$

(c)

${ P }_{ 1 }={ P }_{ 2 }$

(d)

$\cfrac { { P }_{ 1 } }{ { P }_{ 2 } }$

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

(a)

copper

(b)

tungsten

(c)

carbon

(d)

silver

7. The potential difference across the terminals of a cell varies with the current drown from the cell according to the graph.

(a)

(b)

(c)

(d)

8. Resistance between the points A and B in the given figure is

(a)

$9\Omega$

(b)

$2\Omega \quad$

(c)

$3\Omega$

(d)

$6\Omega$

9. Nichrome wire is used as the heating element because it has _____________.

(a)

low specific resistance

(b)

low melting point

(c)

high specific resistance

(d)

high specific resistance

10. Fuse wire is an alloy of

(a)

37 % lead and 63 % tin

(b)

63 % lead and 37 % tin

(c)

37 % copper and 63 % tin

(d)

63 % copper and 37 % tin

11. The ratio of voltage and current in a dosed circuit is _______________.

(a)

decreases

(b)

increases

(c)

remains constant

(d)

varies

12. By increasing the temperature, the specific resistance of a conductor and a semiconductor ___________________.

(a)

increases for both

(b)

increases, decreases respectively

(c)

decreases for both

(d)

decreases, increases respectively

13. Which energy is used to liberate the outer electron from the individual atoms?

(a)

Thermostatic external energy

(b)

Thermodynamic internal energy

(c)

Thermodynamic external energy

(d)

Thermostatic internal energy

14. Melting point of a tungsten filament inside a glass bulb is_________

(a)

3360o C

(b)

3340oC

(c)

3380oC

(d)

3370oC

15. Kirchoff's II law isa consequence of conservation of________

(a)

eharges

(b)

momentum

(c)

energy

(d)

power

16. A potential of 1 kV is applied between the ends of conductor of length 20 cm. The drift velocity of electron in this field is 3.52 x 106 m/s. The relaxation time for the free electrons is

(a)

2 nano sec

(b)

4 nano sec.

(c)

6 nano sec

(d)

8 nano sec.

17. The specific resistance for the insulators is in the range of________

(a)

10-610-8$\Omega m$

(b)

108-1014$\Omega m$

(c)

10-8-10-14$\Omega m$

(d)

10-8-1014$\Omega m$

18. Super conductors can be used as storage elements in_________

(a)

TV

(b)

camera

(c)

computers

(d)

computers

19. The temperature coefficient of resistance increases for the metals when________

(a)

the temperature increases

(b)

the temperature decreases

(c)

does not depend upon the temperature

(d)

either (a) or (b)

20. Kirchhoff's I law is named as_____________

(a)

ohm's law

(b)

voltage law

(c)

resistance law

(d)

current law