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# NCERT Based Test: Magnetic Force

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## 15 Questions MCQ Test Physics Class 12 | NCERT Based Test: Magnetic Force

NCERT Based Test: Magnetic Force for NEET 2023 is part of Physics Class 12 preparation. The NCERT Based Test: Magnetic Force questions and answers have been prepared according to the NEET exam syllabus.The NCERT Based Test: Magnetic Force MCQs are made for NEET 2023 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests for NCERT Based Test: Magnetic Force below.
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NCERT Based Test: Magnetic Force - Question 1

### When a magnetic compass needle is carried nearby to a straight wire carrying current, then (i) the straight wire cause a noticeable deflection in the compass needle. (ii) the alignment of the needle is tangential to an imaginary circle with straight wire as its centre and has a plane perpendicular to the wire

Detailed Solution for NCERT Based Test: Magnetic Force - Question 1

Both points are correct and these are the result of experiments done by Danish physicist Hans Christian Oersted in 1820.

NCERT Based Test: Magnetic Force - Question 2

### Which one of the following is not correct about Lorentz force?

Detailed Solution for NCERT Based Test: Magnetic Force - Question 2

If charge is not moving then the magnetic force is zero.
Since As for stationary charge ∴ .

NCERT Based Test: Magnetic Force - Question 3

### A strong magnetic field is applied on a stationary electron. Then the electron

Detailed Solution for NCERT Based Test: Magnetic Force - Question 3

As As the electron is stationary. ∴ velocity ∴ So, electron will remain stationary.

NCERT Based Test: Magnetic Force - Question 4

In an inertial frame of reference, the magnetic force on a moving charged partic le is Its value in another inertial frame of reference will be

Detailed Solution for NCERT Based Test: Magnetic Force - Question 4 which shows magnetic field is velocity dependent due to which it differs from one intertial frame to another.

NCERT Based Test: Magnetic Force - Question 5

The magnetic force on a current carrying conductor of length l in an external magnetic field is given by

NCERT Based Test: Magnetic Force - Question 6

A straight wire having mass of 1.2 kg and length of 1m carries a current of 5A. If the wire is suspended in mid-air by a uniform horizontal magnetic field, then the magnitude of field is

Detailed Solution for NCERT Based Test: Magnetic Force - Question 6

For mid-air suspension the upward force F on wire due to magnetic field B must be balanced by the force due to gravity, then
IIB = mg; B = mg/II
Here, m = 1.2 kg, g = 10 m s-2, l = 5 A, l = 1m NCERT Based Test: Magnetic Force - Question 7

A circular loop of radius R carrying a current I is placed in a uniform magnetic field B perpendicular to the loop. The force on the loop is

NCERT Based Test: Magnetic Force - Question 8

A 2.5 m long straight wire having mass of 500 is suspended in mid air by a uniform horizontal magnetic field B. If a current of 4 A is passing through the wire then the magnitude of the field is (Take g = 10 m s-2)

Detailed Solution for NCERT Based Test: Magnetic Force - Question 8

Here, m = 500g = 0.5kg, l = 4A, l = 2.5m
As F = IIB sinθ
mg = IIB sin90°, (∵ θ= 90°and F = mg) NCERT Based Test: Magnetic Force - Question 9

A current of 10 A is flowing in a wire of length 1.5 m. A force of 15 N acts on it when it is placed in a uniform magnetic field of 2 T. The angle between the magnetic field and the direction of the current is

Detailed Solution for NCERT Based Test: Magnetic Force - Question 9

F = IlBsinθ or sinθ = F/IlB or θ = 30°

NCERT Based Test: Magnetic Force - Question 10

The horizontal component of earth's magnetic field at a certain place is 3.0 x 10-5 T and having a direction from the geographic south to geographic north. The force per unit length on a very long straight conductor carrying a steady current of 1.2 A in east to west direction is

Detailed Solution for NCERT Based Test: Magnetic Force - Question 10

Force per unit length f = F/l = IB sinθ
when the current is flowing from east to west then θ = 90°, hence
f = IBsin 90° = 1.2 x 3 x 10-5 x 1 = 3.6 x 10-5 N m-1.

NCERT Based Test: Magnetic Force - Question 11

A circular coil of 20 turns and 10 cm radius is placed in a uniform magnetic field of 1.10T normal to the plane of the coil. If the current in the coil is 5A, cross-sectional area is 10-5 m2 and coil is made up of copper wire having free electron density about 1029 m-3, then the average force on each electron in the coil due to magnetic field is

Detailed Solution for NCERT Based Test: Magnetic Force - Question 11

Force on each electron,
evdB = IB/nA Here, I = 5 A, B = 0.1 T, n = 1029 m-3
A = 10-5m2
So, NCERT Based Test: Magnetic Force - Question 12

The magnetic force per unit length on a wire carrying a current of 10 A and making an angle of 45° with the direction of a uniform magnetic field of 0.20 T is

Detailed Solution for NCERT Based Test: Magnetic Force - Question 12

l = 10 A, θ = 45°, B = 0.2 T
∴ F = IlB sin θ
∴ F/l = IB sin 45° = 10 x 0.2 x 1/√2 = 2/√2 N m-1

NCERT Based Test: Magnetic Force - Question 13

An 8 cm long wire carrying a current of 10 A is placed inside a solenoid perpendicular to its axis. If the magnetic field inside the solenoid is 0.3 T, then megnetic force on the wire is

Detailed Solution for NCERT Based Test: Magnetic Force - Question 13

F = lIB sinθ
Here, θ = 900, l = 10 A,
l = 8cm = 8 x 10-2m, B = 0.3T
F = 10 x 8 x 10-2 x 0.3 x sin 900 = 0.24 N

NCERT Based Test: Magnetic Force - Question 14

A rectangular coil ABCD is hung from one side of a balance as shown in figure. A 500 g mass is added to the other arm to balance the weight of the coil. A current of 9.8 A is passed through the coil and a constant magnetic field of 0.4 T acting inward (in xz plane) is switched on such that only arm CD of length 1.5 cm lies in the field. The additional mass m must be added to regain the balance is Detailed Solution for NCERT Based Test: Magnetic Force - Question 14

In absence of magnetic field the weight added in one pan balances the rectangular coil in the other pan of balance,
∴ Mgl = Wcoill or Wcoil = Mg = 0.5 x 9.8 N
When current I is passed through the coil and the magnetic field is switched on.
Let m mass be added in the first pan to regain the balance
Then Mgl + mgl = Wcoil l + IBL sin90° l
mgl = IBLI
or = 6 x 10-3 kg = 6 g

NCERT Based Test: Magnetic Force - Question 15

Which one of the following is correct statement about magnetic forces?

Detailed Solution for NCERT Based Test: Magnetic Force - Question 15

As the action and reaction are instantaneous in IIIrd law. But magnetic forces transmit with finite speed c.

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## Physics Class 12

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