TN SCERT 12th physics 2nd Assignment Answer Key GRLVidya

Unit – 2 CURRENT ELECTRICITY

Part – A

I. One Mark Questions

1.The following graph shows current versus voltage values of some unknown conductor. What is the resistance of this conductor?

(a) 2 ohm

(b) 4 ohm

(c) 8 ohm

(d)1 ohm

Answer:- (a) 2 ohm

2.A toaster operating at 240 V has a resistance of 120 Ω. Its power is

a) 4 0 W

b 2 W

c) 480 W

d) 2 0 W

Answer:- c) 480 W

3.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

Answer:- d) copper decreases and germanium increases

4.In Joule’s heating law, when R and t are constant, if the H is taken along the y axis and I2along the x axis, the graph is

a) straight line

b) parabola

c) circle

d) ellipse

Answer:- a) straight line

5.The resistance of a conductor in the form of a wire depends on its

a) length

b)material

c)diameter

d)temperature

Answer:- a) length

6.Electric Current is rate of change in

a) Electric Potential

b) Electric Charge

c) Electric field

d) Induction

Answer:- b) Electric Charge

7.SI unit of Mobility

Answer:- C m² / V_s

8.Colour of the resister which shows 10% tolerance

a) Gold

b) Silver

c)Brown

d) Colour less

Answer:- b) Silver

9.The terminal voltage of Battery is

a) always less than emf
b) always equal to emf
c) less or equal to emf is depending on the direction of current flow
d) less or equal to emf is depending on internal resistance if the cell

Answer:- a) always less than emf

10.The masses of different substances liberated in electrolysis by the same
quantity of electricity are proportional to their relative

a) atomic masses
b) valencies
c) ratios of atomic masses and valency
d) product of atomic masses and valency

Answer:- d) product of atomic masses and valency

Part – B

II. Very Short Answer

1.Write a short note on superconductors?

The ability of certain metals, their compounds and alloys to conduct electricity with zero resistance at very low temperatures is called superconductivity.

2.Define current density.

3.Define electrical resistivity.

Electrical resistivity of a material is defined as the resistance offered to current flow by a conductor of unit length having unit area of cross section.

4.State Joule’s law of heating.

It states that the heat developed in an electrical circuit due to the flow of current varies directly as:

1. the square of the current
2. the resistance of the circuit and
3. the time of flow.
   H = I²R?

5.What is Seebeck effect?

Seebeck discovered that in a closed circuit consisting of two dissimilar metals, when the junctions are maintained at different temperatures, an emf (potential difference) is developed.

Part – C

III. Short Answer.

1.State and explain Kirchhoff ’s rules.

2.Obtain the condition for bridge balancein Wheatstone’s bridge.

Part – D

IV.Write in detail.

1.Obtain the macroscopic form of Ohm’slaw from its microscopic form
anddiscuss its limitation.

Unit – 3 MAGNETISM AND MAGNETIC EFFECT OF CURRENT

Part – A

I.One Mark Questions

1.The vertical component of Earth’s magnetic field at a place is equal to the
horizontal component. What is the value of angle of dip at this place?

(a) 30^o

(b) 45^o

(c) 60^o

(d) 90^o

Answer:- (b) 45^o

2.

(a) –0.1 J

(b) –0.8 J

(c) 0.1 J

(d) 0.8 J

Answer:- (a) –0.1 J

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

(a) q/ m

(b) 2q/ m

(c) q /2m

(d) q /4m

Answer:- (c) q /2m

4.Three 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. They are placed in a uniform magnetic field and same electric current is passed
through them. Which of the following loop configuration will experience great torque ?

(a) Circle

(b) Semi-circle

(c) Square

(d) All of them

Answer:- (b) Semi-circle

5.A thin insulated wire forms a plane spiral of N = 100 tight turns carrying a current I = 8 m A (milli ampere). The radii of inside and outside turns are a = 50 mm and b = 100 mm respectively. The magnetic induction at the centre of the spiral is

(a) 5 μT

(b) 7 μT

(c) 8 μT

(d) 10 μT

Answer:- (b) 7 μT

6.Magnetic declination of Chennai City is

Answer:- (a) -1⁰16′

7.SI unit of Magnetic Induction is

Answer:- d) NA^-1m^-1

8.The ratio of Magnetic length and Geometrical length

(a) 6/5

(b) 5/6

(c) 8/5

(d) 5/8

Answer:- (b) 5/6

9.Under what conditions Potential energy of the bar magnet is maximum
when it is placed in an external magnetic field

(a) Bar magnet is aligned parallel to the external magnetic field
(b) Bar magnet is aligned anti-parallel to the external magnetic field
(c) Bar magnet is aligned perpendicular to the external magnetic field
(d) none of these

Answer:- (b) Bar magnet is aligned anti-parallel to the external magnetic field

10.According to Curie Law, the graph drawn between magnetic susceptibility and temperature is

(a) a rectangular parabola
(b) a rectangular hyperbola
(c) a circular parabola
(d) a circular hyperbola

Answer:- (b) a rectangular hyperbola

Part – B

II. Very Short Answer.

1.What is meant by magnetic induction?

2.Define magnetic flux

3.Define magnetic dipole moment

4.State Coulomb’s inverse law.

5.What is magnetic susceptibility ?

Part – C

III. Short Answer.

1.What is tangent law? Discuss in detail

2.Discuss Earth’s magnetic field in detail.

Part – D

IV. Write in detail.

Discuss the working of cyclotron in detail.