Magnetism and Matter Test 34

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Magnetism and Matter Test 34

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Question 1
1 / -0

The magnetic flux $$\phi$$ (in weber) in a closed circuit of resistance $$10\ ohm$$ varies with time $$t$$ (in second) according to equation $$\phi=6t^{2}-5t+1$$. The magnitude of induced current at $$t=0.25\ s$$ is:

A
$$1.2\ A$$

B
$$0.8\ A$$

C
$$0.6\ A$$

D
$$0.2\ A$$

Solution
Question 2
1 / -0

Which diagram shows the magnetic field around a bar magnet?

A

B

C

D
Solution
- Two magnetic field lines never interest each other.
- Outside the magnet, the magnetic field lines are directed from North pole of the magnet towards the South pole.
- The magnetic field lines at any one point give the direction of magnetic field at that point
Question 3
1 / -0

Needles $$N_1, N_2$$ and $$N_3$$ are made of a ferromagnetic, a paramagnetic and a diamagnetic substance respectively. A magnet when brought close to them will?

A
Attract all three of them

B
Attract $$N_1$$ strongly, $$N_2$$ weakly and repel $$N_3$$ weakly

C
Attract $$N_1$$ strongly but repel $$N_2$$ and $$N_3$$ weakly

D
Attract $$N_1$$ and $$N_2$$ strongly but repel $$N_3$$

Solution

1)Behaviour in a non- uniform magnetic field -
These are strongly attracted in an external magnetic field (in ferromagnetic substance)
2)Behaviour in a non-uniform magnetic field -
These are feebly attracted in an external magnetic field (in paramagnetic substance)
3)Behaviour in a non-uniform magnetic field -
These are repelled in an external magnetic field. (In diamagnetic substance)
A magnet will attract N1 strongly, N2 weakly and repel N3 weakly.
Question 4
1 / -0

The magnetic flux linked with a coil varies as $$\phi =3t^2+4t+9$$. The magnitude of the emf induced at $$t=2$$ seconds is?

A
$$8$$ V

B
$$16$$ V

C
$$32$$ V

D
$$64$$ V

Solution

$$\phi =\dfrac{d\theta}{dt}$$
$$=6t+4=6(2)+4$$
$$=16V$$.
Question 5
1 / -0

A jet plane having a wing-span of $$25$$ m is travelling horizontally towards east with a speed of $$3600$$ km/hour. If the Earth's magnetic field at the location is $$4\times 10^{-4}$$T and the angle of dip is $$30^o$$, then, the potential difference between the ends of the wing is?

A
$$4$$ V

B
$$5$$ V

C
$$2$$ V

D
$$2.5$$ V

Solution

$$e=B_v/v$$ But $$\dfrac{B_v}{B_H}=lan 30^o=\dfrac{1}{\sqrt{3}}\Rightarrow B_v=\dfrac{4\times 10^{-4}}{\sqrt{3}}T$$
$$\therefore e=\dfrac{4\times 10^{-4}}{\sqrt{3}}\times 25\times\left(3600\times \dfrac{5}{18}\right)=5.77V$$.
Question 6
1 / -0

Curies temperature is the temperature above which :

A
a paramagnetic material becomes ferromagnetic

B
a ferromagnetic material becomes paramagnetic

C
a paramagnetic material becomes diamagnetic

D
a ferromagnetic material becomes diamagnetic

Solution
Question 7
1 / -0

The diagram shows the magnetic field around two bar magnets. Which diagram shows the poles of the magnets?

A

B

C

D

Solution

It is clear that the magnetic line of force starts from N-pole and ends at S-pole.
The diagram in option (C) is correct representation of magnetic line of force.
Question 8
1 / -0

A constant current $$I_{0}$$ is passing through a long straight wire (shown in figure).
A rectangular loop of total resistance $$R$$ is moving parallel to the wire. Then:

A
the heat generated in the loop is with constant rate.

B
current in the loop is zero

C
velocity of loop decreases according to Lenz's law

D
none of the above

Solution

The magnetic flux in the loop remains constant induced emf in the loop is zero.
Hence, induced current in loop is zero.
Question 9
1 / -0

A conducting ring is placed around the core of an electromagnet as shown in figure. When key $$K$$ is pressed, the ring :

A
remains stationary

B
is attracted towards the electromagnet

C
jumps out the core

D
none of the above

Solution

When key $$K$$ is pressed, current through the electromagnet start increasing i.e., flux linked with ring increase which produces repulsion effect. So, it jumps out of the core,
Hence, option C is the answer.
Question 10
1 / -0

Mark correct option or options :

A
Electric field and magnetic field are basically independent

B
Electric field and magnetic field are two aspect of the electromagnetic field

C
Electric field and magnetic field may be produced by charge in rest

D
Both $$(a)$$ and $$(c)$$ are correct

Solution

Electromagnetic waves are transverse in nature as they propagate by varying the electric and magnetic fields such that the two fields are perpendicular to each other. Therefore they are related to each other. And also two aspect of electromagnetic field.