#### Term 1 Model Question Paper

12th Standard EM

Reg.No. :
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Physics

Time : 02:00:00 Hrs
Total Marks : 60
6 x 1 = 6
1. An electric dipole is placed at an alignment angle of 300 with an electric fi eld of 2 × 105 NC-1. It experiences a torque equal to 8 N m. Th e charge on the dipole if the dipole length is 1 cm is

(a)

4 mC

(b)

8 mC

(c)

5 mC

(d)

7 mC

2. 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

3. A carbon resistor of (47 ± 4.7 ) k Ω to be marked with rings of diff erent colours for its identifi cation. Th e 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

4. 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)

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

5. When the current changes from +2A to −2A in 0.05 s, an emf of 8 V is induced in a coil. Th e co-efficient of self-induction of the coil is

(a)

0.2H

(b)

0.4H

(c)

0.8H

(d)

0.1H

6. Which of the following are false for electromagnetic waves

(a)

transverse

(b)

mechanical waves

(c)

longitudinal

(d)

produced by accelerating charges

7. 5 x 1 = 5
8. Air

9. (1)

10. Electric Fuses

11. (2)

Predominantly Inductive

12. RLC circuit

13. (3)

Solar spectrum

15. (4)

εr= 1

16. Fraunhofer Lines

17. (5)

1x10-1m to 1x104m

3 x 2 = 6
18. Assertion: Two surfaces of spheres A and B of radii r1 and r2 when connected by a wire, form an equipotential surface. i.e VA= VB
Reason: Surface charge density (σ) is inversely proportional to the radius of the sphere i.e sx$\frac{1}{r}$. [as radius is smaller, σ will be larger]
(a) Assertion and Reason are correct and Reason is the correct explanation of Assertion.
(b) Assertion and Reason are true but Reason is the false explanation of the Assertion.
(c) Assertion is true but Reason is false.
(d) Assertion is false but Reason is true.

19. Assertion: Kirchoff's voltage rule can be expressed as ${ \varepsilon }_{ 1 }+{ \varepsilon }_{ 2 }+{ \varepsilon }_{ 3 }+...{ \varepsilon }_{ n }={ I }_{ 1 }{ R }_{ 1 }+{ I }_{ 2 }{ R }_{ 2 }+...{ I }_{ n }{ R }_{ n }$
Reason :For the given diagrams

(a) Assertion and Reason are correct and Reason is the correct explanation of Assertion.
(b) Assertion and Reason are true but Reason is the false explanation of the Assertion.
(c) Assertion is true but Reason is False.
(d) Assertion is false but Reason is True

20. Assertion : If two end of a solenoid are bent and together to form a closed ring shape, it is called as toroid
Reason : Magnetic field due to a long current carrying solenoid is m
B=$\frac { \mu NI }{ L }$ =μnI (where, n=$\frac { N }{ L }$)
(a) Assertion and Reason are correct and Reason is the correct explanation of Assertion.
(b) Assertion and Reason are true but Reason is the false explanation of the Assertion.
(c) Assertion is true but Reason is false.
(d) Assertion is false but Reason is true

21. 5 x 2 = 10
22. Define ‘Electric dipole’.

23. State microscopic form of Ohm’s law.

24. Define magnetic flux.

25. State Lenz’s law.

26. What is meant by Fraunhofer lines?

27. 6 x 3 = 18
28. A block of mass m and positive charge q is placed on an insulated frictionless inclined plane as shown in the figure. A uniform electric field E is applied parallel to the inclined surface such that the block is at rest. Calculate the magnitude of the electric field E.

29. Obtain Gauss law from Coulomb’s law.

30. A potential difference across 24 Ω resistor is 12 V. What is the current through the resistor?

31. State and explain Kirchhoff’s rules.

32. What is tangent law? Discuss in detail.

33. How will you define the unit of inductance?

34. 3 x 5 = 15
35. A parallel plate capacitor has square plates of side 5 cm and separated by a distance of 1 mm.
(a) Calculate the capacitance of this capacitor.
(b) If a 10 V battery is connected to the capacitor, what is the charge stored in any one of the plates? (The value of εo = 8.85 x 10-12 Nm2 C-2)

36. Two electric bulbs marked 20 W – 220 V and 100 W – 220 V are connected in series to 440 V supply. Which bulb will be fused?

37. What is the value of x when the Wheatstone’s network is balanced?
P = 500 Ω, Q = 800 Ω, R = x + 400, S = 1000 Ω