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All questions of Electromagnetism for Grade 8 Exam
The magnetic field lines inside a long current-carrying solenoid are near-
- a)Straight
- b)Circular
- c)Elliptical
- d)Parabolic
Correct answer is option 'A'. Can you explain this answer?
The magnetic field lines inside a long current-carrying solenoid are near-
a)
Straight
b)
Circular
c)
Elliptical
d)
Parabolic
|
Gunjan Lakhani answered |
The field lines inside the solenoid are in the form of parallel straight lines. This indicates that the magnetic field is the same at all points inside the solenoid. That is, the field is uniform inside the solenoid.
Magnetic lines of force originate from the- a)North pole
- b)Center point
- c)South pole
- d)Either north pole or south pole
Correct answer is option 'A'. Can you explain this answer?
Magnetic lines of force originate from the
a)
North pole
b)
Center point
c)
South pole
d)
Either north pole or south pole
|
Ananya Das answered |
The direction of magnetic line of force is the direction of force on a North Pole, so the magnetic lines of force always begin on the North Pole of a magnet and end on the South Pole of the magnet. When a small magnetic compass is placed along a lie of force, it sets itself along the line tangential to it. Hence, the line drawn from the South Pole of the compass to its North pole shows the direction of the magnetic field.
An electric current flowing through a conductor produces
- a)Magnetic field
- b)Electric Field
- c)Electromagnetic field
- d)None of these
Correct answer is option 'A'. Can you explain this answer?
An electric current flowing through a conductor produces
a)
Magnetic field
b)
Electric Field
c)
Electromagnetic field
d)
None of these
|
Vikas Kumar answered |
An electric current through a metallic conductor produces a magnetic field around it.
A magnetic field existing around a magnet can be represented by magnetic field lines. Magnetic field lines always form:- a)open loops
- b)closed loops
- c)straight lines
- d)Both closed loops and straight lines
Correct answer is option 'B'. Can you explain this answer?
A magnetic field existing around a magnet can be represented by magnetic field lines. Magnetic field lines always form:
a)
open loops
b)
closed loops
c)
straight lines
d)
Both closed loops and straight lines
|
Krishna Iyer answered |
Magnetic field lines can never cross, meaning that the field is unique at any point in space. Magnetic field lines are continuous, forming closed loops without beginning or end.
Which of the following metal is not attracted by a magnet?- a)Cobalt
- b)Nickel
- c)Steel
- d)Silver
Correct answer is option 'D'. Can you explain this answer?
Which of the following metal is not attracted by a magnet?
a)
Cobalt
b)
Nickel
c)
Steel
d)
Silver
|
|
Ananya Das answered |
In the natural states, metals such as brass, copper , gold and silver will not attract magnets. This is because they are weak metals to start with. Magnets only attach themselves to strong metals such as iron and cobalt and that is why not all types of metals can make magnets stick to them.
Can you explain the answer of this question below:A vertical wire carries a current straight down. To the east of this wire, the magnetic field points:
- A:
eastwards
- B:
downwards
- C:
southwards
- D:
northwards
The answer is c.
A vertical wire carries a current straight down. To the east of this wire, the magnetic field points:
eastwards
downwards
southwards
northwards
|
|
Anjana Khatri answered |
Use the right hand rule. Point your thumb down. Your fingers curl toward the south when you look on the east side of the wire.
Fuse wire used in lighting circuit is of- a)10 A
- b)15 A
- c)2.5 A
- d)5 A
Correct answer is option 'D'. Can you explain this answer?
Fuse wire used in lighting circuit is of
a)
10 A
b)
15 A
c)
2.5 A
d)
5 A
|
|
Krishna Iyer answered |
Fuse is a piece of wire of a material with a very low melting point. When a high current flows through the circuit due to overloading or short circuit, the wire gets heated and melts. As the result, the circuit is broken and current stops flowing. Hence, the current rating of a fuse is 5 A.
Small current in a circuit is detected by- a)Galvanometer
- b)Solenoid
- c)Voltmeter
- d)Fleming’s left hand rule
Correct answer is option 'A'. Can you explain this answer?
Small current in a circuit is detected by
a)
Galvanometer
b)
Solenoid
c)
Voltmeter
d)
Fleming’s left hand rule
|
|
Ananya Das answered |
Galvanometer is used to detect presence of small current in a circuit
On & off switch is provided with- a)Live and Neutral wire
- b)Live wire
- c)Neutral wire
- d)Earth wire
Correct answer is 'B'. Can you explain this answer?
On & off switch is provided with
a)
Live and Neutral wire
b)
Live wire
c)
Neutral wire
d)
Earth wire
|
Aisha Negi answered |
No current flows through the neutral wire , the technical purpose of switching on and off can be accomplished if switch is connected to the neutral wire but it is a greivious safety hazard since switching off would still current flow in the phase wire ( live wire)
Moving two like poles together usually causes a magnet resting on a table to repel and rotate. This occurs because:- a)Like magnetic poles repel
- b)Unlike magnetic poles attract
- c)Both of these
- d)None of these
Correct answer is option 'C'. Can you explain this answer?
Moving two like poles together usually causes a magnet resting on a table to repel and rotate. This occurs because:
a)
Like magnetic poles repel
b)
Unlike magnetic poles attract
c)
Both of these
d)
None of these
|
Ishan Choudhury answered |
Like poles of magnet repel each other and unlike poles of magnet attract each other.
Induced current found to be highest when coil moves- a)At an angle of 45°
- b)At an angle of 20°
- c)Parallel to magnetic field
- d)Right angles to magnetic field
Correct answer is option 'D'. Can you explain this answer?
Induced current found to be highest when coil moves
a)
At an angle of 45°
b)
At an angle of 20°
c)
Parallel to magnetic field
d)
Right angles to magnetic field
|
|
Vikas Kumar answered |
The induced current is found to be the highest when the direction of motion of the coil is at right angles to the magnetic field.
In the domestic electric circuits, the red coloured insulated copper wire is called- a)Neutral wire
- b)Fuse wire
- c)Live wire
- d)Earthing wire
Correct answer is option 'C'. Can you explain this answer?
In the domestic electric circuits, the red coloured insulated copper wire is called
a)
Neutral wire
b)
Fuse wire
c)
Live wire
d)
Earthing wire
|
Neha Patel answered |
The live wire carries current to the appliance at a high voltage. The neutral wire completes the circuit and carries current away from the appliance. The third wire, called the earth wire (green/yellow) is a safety wire and connects the metal case of the appliance to the earth.
When the direction of current through the conductor is reversed, the direction of- a)force is also reversed
- b)force remains same
- c)electromagnetic field is reversed
- d)electric field is also reversed
Correct answer is option 'A'. Can you explain this answer?
When the direction of current through the conductor is reversed, the direction of
a)
force is also reversed
b)
force remains same
c)
electromagnetic field is reversed
d)
electric field is also reversed
|
Drnitin Gopale answered |
Stretch out your hand as per Fleming left-hand rule and then tilt your hand upside down. You can see that the direction of mag field is the same, but the direction of current has reversed as per the question. also, the thumb goes downwards i.e opposite to initial direction. hence, we can see that the direction of force has been reversed.
Assertion (A): The direction of force on a current-carrying conductor placed in a magnetic field depends on the direction of both the current and the magnetic field.Reason (R): When the direction of the current through the conductor is perpendicular to the direction of the magnetic field, the force experienced by the conductor is at its maximum.- a)If both Assertion and Reason are true and Reason is the correct explanation of Assertion
- b)If both Assertion and Reason are true but Reason is not the correct explanation of Assertion
- c)If Assertion is true but Reason is false
- d)If both Assertion and Reason are false
Correct answer is option 'B'. Can you explain this answer?
Assertion (A): The direction of force on a current-carrying conductor placed in a magnetic field depends on the direction of both the current and the magnetic field.
Reason (R): When the direction of the current through the conductor is perpendicular to the direction of the magnetic field, the force experienced by the conductor is at its maximum.
a)
If both Assertion and Reason are true and Reason is the correct explanation of Assertion
b)
If both Assertion and Reason are true but Reason is not the correct explanation of Assertion
c)
If Assertion is true but Reason is false
d)
If both Assertion and Reason are false
|
Kamna Science Academy answered |
- The assertion that the force on a current-carrying conductor in a magnetic field depends on the directions of both the current and the magnetic field is correct. This relationship is described by the right-hand rule for the force on a current-carrying conductor in a magnetic field.
- The reason that the force is maximum when the current is perpendicular to the magnetic field is also correct. This is a fundamental principle of electromagnetism.
- However, the reason does not directly explain why the assertion is true. While it is true that the force is maximum when the current is perpendicular to the magnetic field, this fact alone does not fully explain the dependence of the force on the directions of both the current and the magnetic field. Hence, Option B is the correct answer.
Electromagnet works on- a)Magnetic effect of current
- b)Electric effect of current
- c)Heating effect of current
- d)Chemical effect of current
Correct answer is option 'A'. Can you explain this answer?
Electromagnet works on
a)
Magnetic effect of current
b)
Electric effect of current
c)
Heating effect of current
d)
Chemical effect of current
|
|
Nisha Choudhury answered |
An electromagnet works on the magnetic effect of current. It has been found that if a soft iron rod called core is placed inside a solenoid, then the strength of the magnetic field becomes very large because the iron ore is magnetized by induction.
Which of the following statement concerning magnetic field is correct ?
(1) The part of a bar magnet, at which the magnetic field is the strongest, is called its pole.
(2) A magnetic field is present near a compass needle.
(3) There is no magnetic field inside a current-carrying solenoid.- a)(1) and (2) only
- b)(2) and (3) only
- c)(2) only
- d)(1) only
Correct answer is option 'A'. Can you explain this answer?
Which of the following statement concerning magnetic field is correct ?
(1) The part of a bar magnet, at which the magnetic field is the strongest, is called its pole.
(2) A magnetic field is present near a compass needle.
(3) There is no magnetic field inside a current-carrying solenoid.
(1) The part of a bar magnet, at which the magnetic field is the strongest, is called its pole.
(2) A magnetic field is present near a compass needle.
(3) There is no magnetic field inside a current-carrying solenoid.
a)
(1) and (2) only
b)
(2) and (3) only
c)
(2) only
d)
(1) only
|
Crafty Classes answered |
Statement (1) is correct: A bar magnet has two poles - a north pole and a south pole. The magnetic field is strongest near these poles.
Statement (2) is also correct: A compass needle aligns itself with the Earth's magnetic field, and it points towards the Earth's magnetic north. This indicates the presence of a magnetic field around the Earth.
Statement (3) is incorrect: In fact, a current-carrying solenoid produces a strong magnetic field inside it. The direction of the magnetic field can be determined using the right-hand thumb rule.
Statement (2) is also correct: A compass needle aligns itself with the Earth's magnetic field, and it points towards the Earth's magnetic north. This indicates the presence of a magnetic field around the Earth.
Statement (3) is incorrect: In fact, a current-carrying solenoid produces a strong magnetic field inside it. The direction of the magnetic field can be determined using the right-hand thumb rule.
What happens to the direction of the force on a current-carrying conductor when the direction of the current is reversed, while the magnetic field remains unchanged?- a)The direction of the force remains the same.
- b)The direction of the force is reversed.
- c)The magnitude of the force is doubled.
- d)The force becomes zero.
Correct answer is option 'B'. Can you explain this answer?
a)
The direction of the force remains the same.
b)
The direction of the force is reversed.
c)
The magnitude of the force is doubled.
d)
The force becomes zero.
|
Ciel Knowledge answered |
According to Fleming's left-hand rule, if the direction of the current is reversed while keeping the magnetic field unchanged, the direction of the force on the conductor is also reversed.
The magnetic field inside a long straight solenoid carrying current _____.- a)is zero
- b)decreases as we move towards its end
- c)increases as we move towards its end
- d)is the same at all points
Correct answer is option 'D'. Can you explain this answer?
The magnetic field inside a long straight solenoid carrying current _____.
a)
is zero
b)
decreases as we move towards its end
c)
increases as we move towards its end
d)
is the same at all points
|
Top Rankers answered |
The magnetic field inside a long straight solenoid carrying current is the same at all points. This characteristic is a key property of the magnetic field produced by such a configuration.
If a current-carrying conductor is placed in a uniform magnetic field and oriented parallel to the magnetic field lines, what happens to the force on the conductor?- a)The force is at its maximum.
- b)The force is zero.
- c)The force is doubled.
- d)The force becomes perpendicular to the field.
Correct answer is option 'B'. Can you explain this answer?
If a current-carrying conductor is placed in a uniform magnetic field and oriented parallel to the magnetic field lines, what happens to the force on the conductor?
a)
The force is at its maximum.
b)
The force is zero.
c)
The force is doubled.
d)
The force becomes perpendicular to the field.
|
|
Top Rankers answered |
When a current-carrying conductor is oriented parallel to the magnetic field lines, the force experienced by the conductor is zero. This is because the force on the conductor is given by F=BILsinθ, where θ is the angle between the direction of the current and the magnetic field. When θ is 0 degrees (parallel), sinθ is zero, resulting in no force.
A current-carrying rod experiences a force perpendicular to its length and the ______ field.- a)Electric
- b)Magnetic
- c)Gravitational
- d)Static
Correct answer is option 'B'. Can you explain this answer?
A current-carrying rod experiences a force perpendicular to its length and the ______ field.
a)
Electric
b)
Magnetic
c)
Gravitational
d)
Static
|
EduRev NEET answered |
A current-carrying rod experiences a force perpendicular to its length and the magnetic field, as described by the interaction between current and magnetic fields in electromagnetism.
In which direction does a freely suspended compass needle align itself?- a)North-South
- b)East-West
- c)North-east
- d)North-west
Correct answer is option 'A'. Can you explain this answer?
In which direction does a freely suspended compass needle align itself?
a)
North-South
b)
East-West
c)
North-east
d)
North-west
|
Rohan Kapoor answered |
A freely suspended magnet always points in north - south direction. This is because its south pole is attracted by earth's north pole and the north pole of the magnet is attracted by the earth's south pole. when we hang it freely it automatically starts pointing in north-south direction. The magnetic compass also works on the same principle.
Which of the following statements is true about the magnetic field inside a long, straight solenoid carrying current?- a)The magnetic field is strongest at the ends of the solenoid.
- b)The magnetic field inside the solenoid is uniform and parallel to the axis.
- c)The magnetic field inside the solenoid is zero.
- d)The magnetic field inside the solenoid fluctuates randomly.
Correct answer is option 'B'. Can you explain this answer?
a)
The magnetic field is strongest at the ends of the solenoid.
b)
The magnetic field inside the solenoid is uniform and parallel to the axis.
c)
The magnetic field inside the solenoid is zero.
d)
The magnetic field inside the solenoid fluctuates randomly.
|
Nk Classes answered |
Inside a long, straight solenoid carrying current, the magnetic field is uniform and parallel to the axis of the solenoid. This uniformity is due to the fact that the magnetic field lines are parallel and closely spaced inside the solenoid.
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