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Published on: 13/10/2020
12th Standard Physics Magnetism and magnetic effects of electric current English Medium Free Online Test One Mark questions 2020 - 2021
Download Tamil Nadu 12th Standard Physics question papers, model tests, one-mark questions, important questions, and public exam papers in PDF format. Free study materials and answer keys for TN State Board students.
Questions + Answers key
Take MCQ Physics Test1.
What is the current passing through a coil of radius of 8 cm having 50 turns, when a magnetic intensity at the centre of the coil is 125 A turns m-1?
0.1 ampere
0.4 ampere
1 ampere
4 ampere
2.
Two T.G's having reduction factor K1 and K2 are connected series and give deflections θ1and θ2 respectively. Then K1 : K2 _____________________.
θ 1 : θ 2
tanθ1 : tanθ2
θ 2 : θ 1
tanθ2 : tanθ1
3.
When the number of turns (n) in a galvanometer is doubled, current sensitivity __________________.
remains constant
decreases twice
increases twice
increases four times
4.
Which one of the following pair of particles move with same velocity along the same circular path in a uniform magnetic field?
electron, proton
proton, deutron
proton, alpha particle
deutron, alpha particle
5.
Joule's heating effect and Peltier effect are proportional to the ________________.
square and cube respectively of the current
square and the first power, respectively of the current
square of the current
current
6.
A 110 W, 220 V bulb draws a current _______________.
2 A
440 A
0.5 A
5.5 A
7.
According to Joule's heating effect the law of resistance is _______________.
H ∝ R
H ∝ R2
R ∝ H2
all the above
8.
Fuse wire is _____________.
an alloy of lead and copper
has low resistance
has high resistance
has high melting point
9.
A galvanometer coil has a resistance of 15Ω and gives full-scale deflection for a current of 4mA. To convert it to an ammeter of range 0 to 6 amp ____________.
10mΩ resistance is to be connected in parallel to the galvanometer
10mΩ resistance is to be connected in series with the galvanometer
0.1mΩ resistance is to be connected in series with the galvanometer
0.1mΩ resistance is to be connected in parallel to the galvanometer
10.
The unit of magnetic field is _______________.
ampere-turn
ampere
newton coulomb
tesla
11.
If a current I is flowing in a straight wire parallel to the x-axis and magnetic field is in the y-axis then the wire experiences in _________________.
in Z-direction
in Y- direction
no force
in X- diection
12.
A current carrying conductor is associated with _______________.
electric field
magnetic field
electro magnetic
all these
13.
Which one of the following represents current magnetic field lines?
14.
Which of the following graphs shows the variation of magnetic induction B with distance 'r' from along wire carrying current?
15.
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?
30°
45°
60°
90°
16.
The BH curve for a ferromagnetic material is shown in the figure. The material is placed inside a long solenoid which contains 1000 turns/cm. The current that should be passed in the solenoid to demagnetize the ferromagnet completely is _____.
1.00 m A
1.25 mA
1.50 mA
1.75 mA
17.
A bar magnet of length l and magnetic moment pm is bent in the form of an arc as shown in Figure. The new magnetic dipole moment will be
pm
\(\frac{3}{\pi} p_{m}\)
\(\frac{2}{\pi} p_{m}\)
\(\frac{1}{2} p_{m}\)
18.
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 ______.
\(5\mu T\)
\(7\mu T\)
\(8\mu T\)
\(10\mu T\)
19.
A particle having mass m and charge q accelerated through a potential difference V. Find the force experienced when it is kept under perpendicular magnetic field \(\vec { B } \).
\(\sqrt { \frac { 2{ q }^{ 3 }BV }{ m } } \)
\(\sqrt { \frac { { q }^{ 3 }{ B }^{ 2 }V }{ 2m } } \)
\(\sqrt { \frac { 2{ q }^{ 3 }{ B }^{ 2 }V }{ m } } \)
\(\sqrt { \frac { { 2q }^{ 3 }BV }{ { m }^{ 3 } } } \)
20.
The magnetic field at the centre O of the following current loop is
\(\frac { { \mu }_{ ° }I }{ 4r } \bigotimes \)
\(\frac { { \mu }_{ ° }I }{ 4r } \bigodot \)
\(\frac { { \mu }_{ ° }I }{ 2r } \bigotimes \)
\(\frac { { \mu }_{ ° }I }{ 2r } \bigodot \)
1.
(b)
0.4 ampere
2.
(d)
tanθ2 : tanθ1
3.
(c)
increases twice
4.
(d)
deutron, alpha particle
5.
(b)
square and the first power, respectively of the current
6.
(c)
0.5 A
7.
(a)
H ∝ R
8.
(c)
has high resistance
9.
(d)
0.1mΩ resistance is to be connected in parallel to the galvanometer
10.
(d)
tesla
11.
(a)
in Z-direction
12.
(b)
magnetic field
13.
(d)
14.
(c)
15.
\(tan \ I=\frac{B_V}{B_H}=1\)
∴ I = 45o
16.
(c)
1.50 mA
17.
Magnetic moment,
p'm = ml
From figure, \(l=\frac{\pi r}{3}\)
\(\therefore r=\frac{3l}{\pi}\)
∴ New magnetic moment,
p'm = m x r
\(=m\times \frac{3l}{\pi}=\frac{3}{\pi}ml\)
∴ p'm = \(\frac{3}{\pi}p_m\)
18.
(b)
\(7\mu T\)
19.
Lorentz force F = Bqv
Energy w = qV
Energy is equal to kinetic energy,
\(qV=\frac{1}{2}mv^2\)
\(v=\sqrt { \frac {2qV }{ m } } \)
\(\therefore Lorentz \ force \ F= Bq\times \sqrt \frac{2qV}{m}=\sqrt { \frac { 2{ B }^{ 2 }{ q }^{ 3 }V }{ m } } \)
20.
Magnetic filed at the centre of a circular
loop, B = \(\frac{μ_oI}{2\pi R}\)
From the figure, R =\(\frac{2r}{\pi}\)
\(\therefore B'=\frac{μ_oI}{2\pi \times\frac{2r}{\pi}}=\frac{μ_oI}{4r}\)
\(B'=\frac { { \mu }_{ ° }I }{ 4r } \bigotimes \)
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