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Free download in PDF CBSE Class 11 Physics Short Questions & Answers. Here Gkseries provide Physics Solve Questions and Answers for CBSE Class 11 Students.
41
For measurement of potential difference, a potentiometer is preferred over voltmeter because
[A]
potentiometer does not take current from the circuit.
[B]
potentiometer is cheaper than voltmeter.
[C]
the resistance of potentiometer is less than voltmeter.
[D]
potentiometer is more sensitive than voltmeter.
Answer: potentiometer does not take current from the circuit.
42
Which of the following is wrong? Resistivity of a conductor is
[A]
independent of temperature.
[B]
inversely proportional to temperature.
[C]
independent of dimensions of conductor.
[D]
less than resistivity of a semiconductor.
Answer: independent of temperature.
43
Two cells of emf’s approximately 5 V and 10 V are to be accurately compared using a potentiometer of length 400 cm. [NCERT Exemplar]
[A]
The battery that runs the potentiometer should have voltage of 8 V.
[B]
The battery of potentiometer can have a voltage of 15 V and R adjusted so that the potential drop across the wire slightly exceeds 10 V.
[C]
The first portion of 50 cm of wire itself should have a potential drop of 10 V.
[D]
Potentiometer is usually used for comparing resistances and not voltages.
Answer: The battery of potentiometer can have a voltage of 15 V and R adjusted so that the potential drop across the wire slightly exceeds 10 V.
44
A resistance R is to be measured using a meter bridge. Student chooses the standard resistance S to be 100 Ω He finds the null point at l1 = 2.9 cm. He is told to attempt to improve the accuracy. Which of the following is a useful way? [NCERT Exemplar]
[A]
He should measure l1 more accurately.
[B]
He should change Sto 1000 Ω and repeat the experiment.
[C]
He should change S to 3 Ω and repeat the experiment.
[D]
He should give up hope of a more accurate measurement with a meter bridge.
Answer: He should change S to 3 Ω and repeat the experiment.
45
Consider a current carrying wire current I in the shape of a circle. Note that as the current progresses along the wire, the direction of j (current density) changes in an exact manner, while die current/remain unaffected. The agent that is essentially responsible for is
[A]
source of emf.
[B]
electric field produced by charges accumulated on the surface of wire.
[C]
the charges just behind a given segment of wire which push them just the right way by repulsion.
[D]
the charges ahead.
Answer: electric field produced by charges accumulated on the surface of wire.
46
Which of the following is not correct about cyclotron?
[A]
It is a machine to accelerate charged particles or ions to high energies.
[B]
Cyclotron uses both electric and magnetic fields in combination to increase the energy of charged particles.
[C]
The operation of the cyclotron is based on the fact that the time for one revolution of an ion is independent of its speed or radius of its orbit.
[D]
The charged particles and ions in cyclotron can move on any arbitrary path.
Answer: The charged particles and ions in cyclotron can move on any arbitrary path.
47
A charged particle is moving in a cyclotron, what effect on the radius of path of this charged particle will occur when the frequency of the ratio frequency field is doubled?
[A]
It will remain unchanged.
[B]
It will be increased by four times.
[C]
It will be halved.
[D]
It will also be doubled.
Answer: It will remain unchanged.
48
Two a-particles have the ratio of their velocities as 3 : 2 on entering the field. If they move in different circular paths, then the ratio of the radii of their paths is
[A]
3 : 2
[B]
4 : 9
[C]
2 : 3
[D]
9 : 4
49
A charged particle is moving on circular path with velocity v in a uniform magnetic field B, if the velocity of the charged particle is doubled and strength of magnetic field is halved, then radius becomes
[A]
8 times
[B]
4 times
[C]
2 times
[D]
None of these
50
Which one of the following is correct statement about magnetic forces?
[A]
Magnetic forces always obey Newton’s third law.
[B]
Magnetic forces do not obey Newton’s third law.
[C]
For very high current, magnetic forces obey Newton’s third law.
[D]
Inside low magnetic field, magnetic forces obey Newton’s third law.
Answer: Magnetic forces do not obey Newton’s third law.
51
In an inertial frame of reference, the magnetic force on a moving charged particle is Its value in another inertial frame of reference will be
[A]
remained same
[B]
changed due to change in the amount of charge
[C]
changed due to change in velocity of charged particle
[D]
changed due to change in field direction
Answer: changed due to change in velocity of charged particle
52
A strong magnetic field is applied on a stationary electron. Then the electron
[A]
moves in the direction of the field.
[B]
remained stationary.
[C]
moves perpendicular to the direction of the field.
[D]
moves opposite to the direction of the field.
Answer: remained stationary.
53
A positive charge enters in a magnetic field and travels parallel to but opposite the field. If experiences
[A]
an upward force.
[B]
a downward force.
[C]
an accelerated force.
[D]
no force.
Answer: an accelerated force.
54
An electron is projected along the axis of a circular conductor carrying the same current. Electron will experience
[A]
a force along the axis
[B]
a force perpendicular to the axis.
[C]
a force at an angle of 4° with axis.
[D]
no force experienced.
Answer: no force experienced.
55
The gyro-magnetic ratio of an electron in an H-atom, according to Bohr model, is
[A]
independent of which orbit it is in.
[B]
neutral
[C]
positive
[D]
increases with the quantum number n.
Answer: independent of which orbit it is in.
56
A conducting circular loop of radius r carries a constant current i. It is placed in a uniform magnetic field B, such that B is perpendicular to the plane of the loop. The magnetic force acting on the loop is
[A]
irB.
[B]
2πriB
[C]
zero
[D]
πriB
57
If the beams of electrons and protons move parallel to each other in the same direction, then they
[A]
attract each other.
[B]
repel each other.
[C]
no relation.
[D]
neither attract nor repel.
Answer: repel each other.
58
A current loop placed in a non-uniform magnetic field experiences
[A]
a force of repulsion.
[B]
a force of attraction.
[C]
a torque but not force.
[D]
a force and a torque.
Answer: a force and a torque.
59
The maximum current that can be measured by a galvanometer of resistance 40 Ω is 10 mA. It is converted into voltmeter that can read upto 50 V. The resistance to be connected in the series with the galvanometer is
[A]
4960 Ω
[B]
5040 Ω
[C]
4050 Ω
[D]
2010 Ω
60
A current carrying closed loop of an irregular shape lying in more than one plane when placed in uniform magnetic field, the force acting on it
[A]
will be more in the plane where its larger position is covered.
[B]
is zero.
[C]
is infinite.
[D]
may or may not be zero.
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