12th Physics English Medium 2nd Assignment (with Answers) for July 2021 :- This is the second assignment for 12th standard physics subject english medium with answers
Class: XII Subject: PHYSICS
Unit – 2 CURRENT ELECTRICITY
Part – A
I.One Mark Questions
1.The following graph shows currentversus voltage values of some
unknownconductor. What is the resistance ofthis conductor?
(a) 2 ohm
(b) 4 ohm
(c) 8 ohm
Answer:- (a) 2 ohm
2.A toaster operating at 240 V has aresistance 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 ofgermanium are cooled from roomtemperature to 80 K. The resistance of
a) each of them increases
b) each of them decreases
c) copper increases and germaniumdecreases
d) copper decreases and germaniumincreases
Answer:- d) copper decreases and germanium increases
4.In Joule’s heating law, when R and t areconstant, if the H is taken along
the yaxis and I2along the x axis, the graph is
a) straight line
Answer:- a) straight line
5.The resistance of a conductor in the form of a wire depends on its
Answer:- a) length
6.Electric Current is rate of change in
a) Electric Potential
b) Electric Charge
c) Electric field
Answer:- b) Electric Charge
7.SI unit of Mobility
Answer:- C m2 / Vs
8.Colour of the resister which shows 10% tolerance
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
c) ratios of atomic masses and valency
d) product of atomic masses and valency
Answer:- d) product of atomic masses and valency
P rt – 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:
- the square of the current
- the resistance of the circuit and
- 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 MAGNAETISM 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?
Answer:- (b) 45o
(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 uniffrm magnetic field and same electric current is passed
through them. Which of the fllowin loop configuration will experience
greate torque ?
(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
(a) (b) (c) (d)
Answer:- d) NA-1m-1
8.The ratio of Magnetic length and Geometrical length
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